As much as I love spears and halberds... I have to go hidden blades.
(psst: clubs, tomahawks, bow and arrows, rope darts, muskets and pistols seem to have missed the list -- basically, AC3)
EDIT: didn't realize this was the ACR forum, my bad... I only ever look at recent posts and thought this would be a good question for overall in the series....
“Force has no place where there is need of skill." Herodotus
If it makes you feel any better I almost clarified that this was just for Revelations and prior before I even finished reading your post 
I have a feeling that hidden blades will dominate on this poll, and rightfully so!
I like axes cause they work the best against Janissaries and unlike ACB they actually kill streak well.
The Almogavar Axe is absolutely deadly against any foe, be it Janissaries, Varangians, Agiles, or just Elites.
if you're good at combat (like me 
) you can just kill Janissaries for fun in sequence 2 (wink wink).