1. About Ubuntu's mouse bug:
It also appears in the map editor(quite often) and very very rarely it appears in the menus.
2. Laser bug in 0.5:
If the laser is shot very flat to the ground, it bounces back into your direction, instead of away from you.
Screenshot: http://img187.imageshack.us/img187/32/s … 004cy3.png
3. A strange hook bug in 0.5:
If you hook at a wall, and you release the hook again, sometimes it happens, that your hook is not released immediatly. It is not much time you lose, but the direction you fly then is different. So if you know, how the hook behaves normally, you notice it, and its very annoying.