R u up to some mind twisting logic problems??! Here are some:

http://rec-puzzles.org/logic.html
not all of them are cool, but make sure u check these out:
-children
-smullyan/black.hat
-smullyan/fork.three.men
-smullyan/integers (toughest yet coolest,,
and note explanation is more important than actual answer)
-unexpected (REAL cool philosophy)

[not all puzzles are solvable, some of them are only
there to show a point]

another very tough (REAL tough this time)
puzzle is here