wktask - Windows Mobile would not be the same without it, IMO.
wvd - for my sporadic pr0n streaming needs
quick menu
s2p, s2v
capsure
kinoma - it's Orb feature is pretty useful
PocketPuTTY
mochaVNC
Twikini
I honestly could not function without these apps, so IMO, they are indeed---"Must Have(s)".