Bloxorz!
 

Not sure if this has ever been posted here, but this is one of the coolest flash games I've ever played...

You have to manuver a rectangular block through a series of levels. One slip and you have to start the level over.

"http://www.bass10.com/flash-games/puzzle-games/bloxorz-puzzle-game/

Totally addictive.... Try it! :thumbup: