Most: Junker
Least: Spire (flown it maybe once in the entire time I've played)
Also for all the Least: Mobule people- Get out and try it!
Not guaranteeing you'll love it, but at least half of you will. Basically you get three guns on the enemy at all times (if not then you need to switch to guns with better arc), kill first, repair later. It's a totally different style of gameplay and I'm still trying to get better at making calls in it (should we stay farther away, go in and brawl?) but I love it.
Plus- every player gets a gun so it's easier to play with all engineer because no one gets stuck as "main". (Same goes for trifecta Junker)