Best Firefox extensions

Everybody gets to do it once in a while, so here's my list of currently in use extensions:

• Adblock
• Tabbrowser extension

I also like the Developpers' toolbar, Image Zoom, and View in IE (for those times when it won't work in Gecko), but I haven't installed them yet, even though I'm still using the old profile.
As soon as the following functionality of TBE is incorporated to Firefox I'll probably stop using TBE:

• Single Window Mode
• Undo close tab
• Double click to close tab (or the corresponding UI)