RuneQuest

There's a highly biased history of this superb RPG at Aesc's RQ Page.

Unfortunately, it looks like Mongoose Publishing are working on a 4th edition as I write this. As they're a d20 house which has managed to completely screw up Judge Dredd, I don't think their version is necesarily a good thing.

Update: Now I've seen the finished item I'm convinced it's not a good thing.