diff --git a/README.md b/README.md
index c2f7195..18ee53c 100644
--- a/README.md
+++ b/README.md
@@ -188,6 +188,29 @@ Valitron\Validator::addRule('alwaysFail', function($field, $value, array $params
 }, 'Everything you do is wrong. You fail.');
 ```
 
+You can also use one-off rules that are only valid for the specified
+fields. 
+
+```php
+$v = new Valitron\Validator(array("foo" => "bar"));
+$v->rule(function($field, $value, $params, $fields) {
+    return true;
+}, "foo")->message("{field} failed...");
+```
+
+This is useful because such rules can have access to variables
+defined in the scope where the `Validator` lives. The Closure's
+signature is identical to `Validator::addRule` callback's
+signature. 
+
+If you wish to add your own rules that are not static (i.e.,
+your rule is not static and available to call `Validator` 
+instances), you need to use `Validator::addInstanceRule`. 
+This rule will take the same parameters as 
+`Validator::addRule` but it has to be called on a `Validator`
+instance.
+
+
 ## Alternate syntax for adding rules
 
 As the number of rules grows, you may prefer the alternate syntax
diff --git a/src/Valitron/Validator.php b/src/Valitron/Validator.php
index 7c76738..4a1a49a 100644
--- a/src/Valitron/Validator.php
+++ b/src/Valitron/Validator.php
@@ -37,6 +37,21 @@ class Validator
      */
     protected $_labels = array();
 
+    /**
+     * Contains all rules that are available to the current valitron instance.
+     *
+     * @var array
+     */
+    protected $_instanceRules = array();
+
+    /**
+     * Contains all rule messages that are available to the current valitron
+     * instance
+     *
+     * @var array
+     */
+    protected $_instanceRuleMessage = array();
+
     /**
      * @var string
      */
@@ -503,7 +518,7 @@ class Validator
         foreach ($this->validUrlPrefixes as $prefix) {
             if (strpos($value, $prefix) !== false) {
                 $host = parse_url(strtolower($value), PHP_URL_HOST);
-                
+
                 return checkdnsrr($host, 'A') || checkdnsrr($host, 'AAAA') || checkdnsrr($host, 'CNAME');
             }
         }
@@ -921,8 +936,9 @@ class Validator
                 }
 
                 // Callback is user-specified or assumed method on class
-                if (isset(static::$_rules[$v['rule']])) {
-                    $callback = static::$_rules[$v['rule']];
+                $errors = $this->getRules();
+                if (isset($errors[$v['rule']])) {
+                    $callback = $errors[$v['rule']];
                 } else {
                     $callback = array($this, 'validate' . ucfirst($v['rule']));
                 }
@@ -945,6 +961,26 @@ class Validator
         return count($this->errors()) === 0;
     }
 
+    /**
+     * Returns all rule callbacks, the static and instance ones.
+     *
+     * @return array
+     */
+    protected function getRules()
+    {
+        return array_merge($this->_instanceRules, static::$_rules);
+    }
+
+    /**
+     * Returns all rule message, the static and instance ones.
+     *
+     * @return array
+     */
+    protected function getRuleMessages()
+    {
+        return array_merge($this->_instanceRuleMessage, static::$_ruleMessages);
+    }
+
     /**
      * Determine whether a field is being validated by the given rule.
      *
@@ -952,6 +988,7 @@ class Validator
      * @param  string  $field The name of the field
      * @return boolean
      */
+
     protected function hasRule($name, $field)
     {
         foreach ($this->_validations as $validation) {
@@ -965,6 +1002,31 @@ class Validator
         return false;
     }
 
+    protected static function assertRuleCallback($callback)
+    {
+        if (!is_callable($callback)) {
+            throw new \InvalidArgumentException('Second argument must be a valid callback. Given argument was not callable.');
+        }
+    }
+
+
+    /**
+     * Adds a new validation rule callback that is tied to the current
+     * instance only.
+     *
+     * @param string                     $name
+     * @param mixed                         $callback
+     * @param string                     $message
+     * @throws \InvalidArgumentException
+     */
+    public function addInstanceRule($name, $callback, $message = null)
+    {
+        static::assertRuleCallback($callback);
+
+        $this->_instanceRules[$name] = $callback;
+        $this->_instanceRuleMessage[$name] = $message;
+    }
+
     /**
      * Register new validation rule callback
      *
@@ -973,27 +1035,75 @@ class Validator
      * @param  string                    $message
      * @throws \InvalidArgumentException
      */
-    public static function addRule($name, $callback, $message = self::ERROR_DEFAULT)
+    public static function addRule($name, $callback, $message = null)
     {
-        if (!is_callable($callback)) {
-            throw new \InvalidArgumentException('Second argument must be a valid callback. Given argument was not callable.');
+        if ($message === null)
+        {
+            $message = static::ERROR_DEFAULT;
         }
 
+        static::assertRuleCallback($callback);
+
         static::$_rules[$name] = $callback;
         static::$_ruleMessages[$name] = $message;
     }
 
+    public function getUniqueRuleName($fields)
+    {
+        if (is_array($fields))
+        {
+            $fields = implode("_", $fields);
+        }
+
+        $orgName = "{$fields}_rule";
+        $name = $orgName;
+        $rules = $this->getRules();
+        while (isset($rules[$name]))
+        {
+            $name = $orgName . "_" . rand(0, 10000);
+        }
+
+        return $name;
+    }
+
+    /**
+     * Returns true if either a valdiator with the given name has been
+     * registered or there is a default validator by that name.
+     *
+     * @param string    $name
+     * @return bool
+     */
+    public function hasValidator($name)
+    {
+        $rules = $this->getRules();
+        return method_exists($this, "validate" . ucfirst($name))
+            || isset($rules[$name]);
+    }
+
     /**
      * Convenience method to add a single validation rule
      *
-     * @param  string                    $rule
+     * @param  string|callback           $rule
      * @param  array                     $fields
      * @return $this
      * @throws \InvalidArgumentException
      */
     public function rule($rule, $fields)
     {
-        if (!isset(static::$_rules[$rule])) {
+        // Get any other arguments passed to function
+        $params = array_slice(func_get_args(), 2);
+
+        if (is_callable($rule)
+            && !(is_string($rule) && $this->hasValidator($rule)))
+        {
+            $name = $this->getUniqueRuleName($fields);
+            $msg = isset($params[0]) ? $params[0] : null;
+            $this->addInstanceRule($name, $rule, $msg);
+            $rule = $name;
+        }
+
+        $errors = $this->getRules();
+        if (!isset($errors[$rule])) {
             $ruleMethod = 'validate' . ucfirst($rule);
             if (!method_exists($this, $ruleMethod)) {
                 throw new \InvalidArgumentException("Rule '" . $rule . "' has not been registered with " . __CLASS__ . "::addRule().");
@@ -1001,10 +1111,8 @@ class Validator
         }
 
         // Ensure rule has an accompanying message
-        $message = isset(static::$_ruleMessages[$rule]) ? static::$_ruleMessages[$rule] : self::ERROR_DEFAULT;
-
-        // Get any other arguments passed to function
-        $params = array_slice(func_get_args(), 2);
+        $msgs = $this->getRuleMessages();
+        $message = isset($msgs[$rule]) ? $msgs[$rule] : self::ERROR_DEFAULT;
 
         $this->_validations[] = array(
             'rule' => $rule,
diff --git a/tests/Valitron/ValidateAddInstanceRuleTest.php b/tests/Valitron/ValidateAddInstanceRuleTest.php
new file mode 100644
index 0000000..ddefac3
--- /dev/null
+++ b/tests/Valitron/ValidateAddInstanceRuleTest.php
@@ -0,0 +1,120 @@
+<?php
+use Valitron\Validator;
+
+function callbackTestFunction($item, $value)
+{
+	return $value === "bar";
+}
+
+class ValidateAddInstanceRuleTest extends BaseTestCase
+{
+    protected function assertValid($v)
+    {
+        $msg = "\tErrors:\n";
+        $status = $v->validate();
+        foreach ($v->errors() as $label => $messages)
+        {
+            foreach ($messages as $theMessage)
+            {
+                $msg .= "\n\t{$label}: {$theMessage}";
+            }
+        }
+
+        $this->assertTrue($v->validate(), $msg);
+    }
+
+    public function testAddInstanceRule()
+    {
+        $v = new Validator(array(
+            "foo" => "bar",
+            "fuzz" => "bazz",
+        ));
+
+        $v->addInstanceRule("fooRule", function($field, $value)
+        {
+            return $field !== "foo" || $value !== "barz";
+        });
+
+        Validator::addRule("fuzzerRule", function($field, $value)
+        {
+            return $field !== "fuzz" || $value === "bazz";
+        });
+
+        $v->rule("required", array("foo", "fuzz"));
+        $v->rule("fuzzerRule", "fuzz");
+        $v->rule("fooRule", "foo");
+
+        $this->assertValid($v);
+    }
+
+    public function testAddInstanceRuleFail()
+    {
+        $v = new Validator(array("foo" => "bar"));
+        $v->addInstanceRule("fooRule", function($field)
+        {
+            return $field === "for";
+        });
+        $v->rule("fooRule", "foo");
+        $this->assertFalse($v->validate());
+    }
+
+    public function testAddAddRuleWithCallback()
+    {
+        $v = new Validator(array("foo" => "bar"));
+        $v->rule(function($field, $value) {
+            return $field === "foo" && $value === "bar";
+        }, "foo");
+
+        $this->assertValid($v);
+    }
+
+    public function testAddAddRuleWithCallbackFail()
+    {
+        $v = new Validator(array("foo" => "baz"));
+        $v->rule(function($field, $value) {
+            return $field === "foo" && $value === "bar";
+        }, "foo");
+
+        $this->assertFalse($v->validate());
+    }
+
+    public function testAddAddRuleWithCallbackFailMessage()
+    {
+        $v = new Validator(array("foo" => "baz"));
+        $v->rule(function($field, $value) {
+            return $field === "foo" && $value === "bar";
+        }, "foo", "test error message");
+
+        $this->assertFalse($v->validate());
+    $errors = $v->errors();
+        $this->assertArrayHasKey("foo", $errors);
+        $this->assertCount(1, $errors["foo"]);
+        $this->assertEquals("Foo test error message", $errors["foo"][0]);
+    }
+
+	public function testAddRuleWithNamedCallbackOk()
+	{
+		$v = new Validator(array("bar" => "foo"));
+		$v->rule("callbackTestFunction", "bar");
+		$this->assertFalse($v->validate());
+	}
+
+	public function testAddRuleWithNamedCallbackErr()
+	{
+		$v = new Validator(array("foo" => "bar"));
+		$v->rule("callbackTestFunction", "foo");
+		$this->assertTrue($v->validate());
+	}
+
+    public function testUniqueRuleName()
+    {
+        $v = new Validator(array());
+        $args = array("foo", "bar");
+        $this->assertEquals("foo_bar_rule", $v->getUniqueRuleName($args));
+        $this->assertEquals("foo_rule", $v->getUniqueRuleName("foo"));
+
+        $v->addInstanceRule("foo_rule", function() {});
+        $u = $v->getUniqueRuleName("foo");
+        $this->assertRegExp("/^foo_rule_[0-9]{1,5}$/", $u);
+    }
+}