I liked Armour Lock, but my favourite would actually be Sprint.
In real life despite my heavy build I have pretty damn mean sprint. This big guy even got 1st place in a official 100M race one time, hard to believe. There were all these athletic lighter guys but I won, I guess I just have more raw power in my legs.
But anyway yea I like Sprint the most. It's been a life saver for me in Halo.