I am annoyed by Flash. It sucks, it is used for annoying stuff everywhere, it hogs cpu cycles like no tomorrow and crashes often. ClickToFlash to the rescue!
Replaces all things Flash by a box that you can click on if you really want to. But what is totally awesome is that it lets you play YouTube videos as H.264 using QuickTime X just inside your (Webkit)-browser using HTML5. It just rocks, essential install.