Skalman said:
The one used in Crysis, can't remember what it's called.
It's called CryEngine, I believe.
I voted for Source. It's far from being top of the notch these days, but it still looks kind of pretty and is old enough to run really, really smooth whatever game/rig combo you may throw at it. That's a feature which is easy to miss, which it is for the most part. Devs, stop your attempts with cutting-edge graphics. You can use an engine like this and concentrate on the actual GAME, that would be great, thank you.
I also think it has a lot of flexibility going for it. Want a regular FPS? Go for it. Want close-up shots of characters? There's hardly anything better. (That's a huuuge advantage it has over Unreal Engine 3, I believe. It's shadowing is not suitable for displaying shadows on close ups at all, cp. Mass Effect, and can't do some other things that can be important)
One thing on the CryEngine - I guess it really sucks

I mean, the visuals are just STUNNING, there's nothing to say against that. But the fact that no one besides Crytek actually seems to USE it tells its own tale. And from what I see, Crysis is MEANT as a slightly upgraded tech demo rather than an actual game, so...