MyBB Codes

List your favorite MyBB plugin(s) here.

Mine:
AJAX PM Notification (if you haven't tried it, trust me this is one of the best ones out there)
AdStats
Download Emails
PM Admin (read your member's PMs, can help immensely)
ezGallery
InfoBar
iShare
Profile Comments
Cannot Send PMs to Self

I could go on and on and on and on....
lol, I have 30+ plugins installed to date

Me infobar

These are my favorites.

AJAX PM Notifications.
Min Post for downloading Attachments
Overview
Ishare
UA Quick Theme
Facebook Like Button
Fit On Page