Go Bananas is another one of those games which is a perfect time killer for on a train or bus. The concept is real simple - you control a slingshot and must fire rocks at the bananas that are scrolling along the top of the tree canopy. Of course - things get spiced up a bit as among the bananas are coconuts. Hit one of these and you lose a life. Hit three and it's game over I'm afraid.
There are three versions of the game - The classic one, an advance one - which has two rows of bananas and coconuts and also a timer version. The advance one is real hard!
This version of the game is free but there is a pro edition too - although I have no idea what extra features you get, so go and grab the free one from the link below.