How do you make a grenade stick to different surfaces?

Hello! I have fps and I am wanting to make grenades. I have them throwing right but I want them to stick to enemies but just bounce off walls and boxes and such. I have a script but it just sticks to rigidbodies. I want it to stick only to enemies, and currently they are not rigidbodies. I am not the best coder in the world so i'd like some help.

Thanks in advance!

 /// This script requires that a rigdibody is attached to the same game object
 
 private var localAttachmentPoint = Vector3.zero;
 private var attachedTransform : Rigidbody;
 private var isAttached = false;
 
 // Enable only when we have a collision
 function Awake ()
 {
     enabled = false;
 }
 
 function OnCollisionEnter ( col : Collision)
 {
     if (isAttached)
         return;
     isAttached = true;
 
     // When we hit a rigidbody we attach to it with a fixed joint
     // this gives extra realism eg. the grenade's mass will now pull down the attached to rigidbody
     if (col.rigidbody)
     {
         var joint = gameObject.AddComponent("FixedJoint");
         joint.connectedBody = col.rigidbody;
     }
     // When we hit a normal collider we just follow the transform around!
     
     else
     {
         // Store local attachment point and transform we stick to    
         attachedTransform = col.rigidbody;
         localAttachmentPoint = attachedTransform.InverseTransformPoint(rigidbody.position);
     
         // The grenade's position is now driven by the script instead of physics
         rigidbody.isKinematic = true;
         enabled = true;
     }
 }
 
 function Update ()
 {
     // Update position to follow the object we stick to
     if (attachedTransform)
     {
         transform.position = attachedTransform.TransformPoint(localAttachmentPoint);
     }
     else
     {
         // The attached transform was destroyed. Let go and enable physics control
         rigidbody.isKinematic = false;
         enabled = false;
     }
 }