most of the ones worth owning or playing have already been mentioned so i'll go a little to the left and say if you have the capability to play imports than definitely DEFINITELY get klaymen klaymen, better known to most people on this side of the world as "The Neverhood"
you can probably get it on pc for dirt cheap or import the japanese copy since it was only released there, i'm pretty sure its 2.5d but ehh fuck it, semantics or no, this game is incredible and very import friendly