AdBlock Plus
AdBlock Plus Pop-up Blocker
HTTPS Everywhere
Lightshot
Multiple Tab Handler
NoScript
Pearltrees
Ponify
Switch to tab no more
Undo closed tab button
I also like to have a Youtube repeater addon, and a Youtube quality manager of some sort.
Adblock Plus (adblocker) Adblock Plus Hiding Helper (adon for ^ (you can use this to "snipe" sidebar ads or logos w/e any image even on websites you regularly visit. Last PassLogs you in to websites automatically and much more, never have to type username and password again!
and *awkward cough*torrent search*awkward cough*