"Boy grabs sled. Boy rides sled. A simple concept yields endless fun and the latest Internet Phenomenon is born!"... I couldn't have put it better myself! MASSIVE success in 2007, Line Rider is the classic tale of a humble web game turned global phenomenon! Has to be played to be understood. Quite simply HOURS of fun.
i played Free Rider 2 its really fun
http://www.thegameslist.com/game/65/Free_Rider_2