I think the world could use a few more good Sokoban clones. It's such an old and well-known concept, and so often copied - yet virtually none of the clones actually expand on the idea and do anything very inventive with it. There's really only "Mole Mania" (which incidentally, is the best puzzle game ever made). There's so much more that could be done with the genre...
Anyway, here's a simple example:
Only the blocks slide on the ice (not the player), but it should be fairly clear how you could make that happen, and how the same basic method could work for conveyor belts etc.