I don't know why we don't see levels tilting more often, this used to be done in 2d platform games but we don't see it very often in 3d games. It would be 'cool' to have a (in-game) building tip sideways and have the player and objects in it start sliding sideways.

That sounds like an awful lot of physics. I remember it being a very impressive effect in Time Crisis 3, though. It seems to me that a game like Half-Life 2 or Psi-Ops, which seem to use a great deal of physics for bery mindane things, might be able to use such a technique rather effectively.

What, though, is a good excuse for it? TC3 did it in a tanker ship that had been bombed. That made sense. But you can't be in a capsizing craft all the time. Could a building tip? Not really. A bus crash would be too quick. Maybe some kind of parallel universe/escher painting would make you feel like David Bowie in Labyrinth, but that isn't quite the same thing.

It's super-cool, from a gameplay perspective, but a little tough to incorporate, I think.

I'm tempted to go crazy with tesserae now, but I'll control myself.

S-S-S-S-Super Monkey Ball :-)

Similar things have been done in space based FPS's where a capitol ship's artificial gravity goes out etc.