I've been a martial arts instructor for about 8 years now, and have studied a pretty large range of styles from modern combatives to more traditional Eastern styles.    I have to agree with Agravaine's post about the key to fighting multiple opponents is to use them as obstacles.  I am going to assume this is some type of self defense situation, because keys aren't a very good sparring weapon? 

How I would handle a situation like that, is first figure out where the escape route would be.  Try to move that direction as much as possible, while making certain none of the opponents get between me and that path.  Throw the keys underhanded/sidearm (almost like throwing a frisbee) at the persons face/neck area while rushing forward.  If it hits, it hurts, and may cut, it's not going to "take someone out" but its a very good distraction.  While rushing in try to get the person you distracted in a hold with their head lower than you, but still standing, so that you can move them around keeping the person trapped in between you and the other people.  While doing this, throw knees and punches to the persons torso area, and then shove them into the next closest person and run towards the escape route you figured out earlier screaming "Take him to the Hospital!".  People will stop to check out their friend, whether they actually need to get medical attention or not. 

The main focus is to keep them from working together until the point that their cooperation is no longer focused on you.