Must have extensions for Thunderbird?

Just curious what extensions other Thunderbird users use?

Here's what I use frequently:
-- Enigmail for encryption (requires GnuPG too)
-- Lightning for calendar
-- MinToTray revived (MinTrayR) because I like to minimize/close Thunderbird to system tray instead of Taskbar
-- LookOut just so certain types of attachments are displayed correctly

Others I have but probably never use:
-- Test Pilot for Thunderbird (I think this came with the installer)
-- MathML-fonts
-- Zoom Button for Thunderbird

Extensions I need or considering:
-- Better search function for searching through emails. Any suggestions? I like how search works in google webmail, but not so much in Thunderbird
-- BitMessange add-on. I don't use BitMessage at the moment, but it sounds good, so I'll probably get on it at some point.

 

Some extensions which I use not mentioned by you:

Auto Resize Image
Collapsed Unread
FiltaQuilla
JunQuilla
Mark All Read Button
Quick Folders
Remove Duplicate Messages
Slideshow

 

Another two ones which I find rather useful:

Manually Sort Folders
No Message Pane Sorting by Mouse