Another one from the group I'm not part of but hear stories about:

The group has just finished killing a vampire spawn. It took them a while, but they did kill it and it turns into mist and vanishes. This ring falls out of the mist, as well as some other stuff. The party argues over the stuff and the rogue picks up the ring.
DM: You feel compelled to put the ring on. Roll a Will save.
Rogue: *Rolls, gets natural 20* I pass.
DM: You stop wanting to put the ring on. It starts whispering to you.
Ring: Put me on. You know you want to.
Rogue: Well, I'm not sure...
Ring: Come on! You want to be powerful, don't you? You want to have magical powers, don't you?
Rogue: Well, yeah, but...
Ring: Then do it! Go ahead, put me on!
Rogue: Ok. *puts it on*

So then he becomes a vampire spawn. He only has control of his actions because he passed the original will save, and the ring is quite obviously cursed. Well, no taking it off for him. The rest of the party thinks they should kill him and spare the world from him, and he's arguing that he's still in control. Then they get attacked by a bunch of orcs and the rogue takes them all on in single combat, and ends up killing three of the four. By himself. Needless to say, the party is freaked about this. In the end, they decide to cut the finger that has the ring on it off. Best part is, the rogue is a halfling. So, OOC, everyone calls him "Frodo of the Nine Fingers"