Just had this pointed out to me.

The Automated Online Role-Player

What happened when someone set up a bot to control a character with the following simple rules:
1. Join any group that invites you
2. When in a group, follow behind the leader
3. Attack any monster you see
4. Accept all trade requests from other players, then give them a melon

I'm sure it's more effective than some real people I've gamed with - at least it acts consistently!