Going by the number of 50s I have, Brutes narrowly edge out all the others. I have more Brutes at 50 than any other archetype, and I'll admit, the sheer adrenalin rush of "smashy smashy SMASHY!" is just awesome. Dual Blades, for some reason, was a personal favorite powerset. Moving from combo to combo to combo just always felt so Zen.
Then Masterminds and Scrappers tie for second; I'll never forget the time my Grave Knights knocked a Button Man into the air and his foot caught in some geometry, leaving him dangling upside down at half health. The "Zombie Pinata" didn't last long, but his memory will live forever.
I also have fond memories of the time I ran into Manticore, and he started his attack by saying, "Bring it on. I've got enough arrows for everybody." Then my Thugs/Dark MM popped Gang War and dropped her Dark Servant. Turned out that strictly speaking, Manticore wasn't 100% accurate there.
Scrappers, of course, are the vanilla ice cream of the game. They go well with everything.
After that...got a couple tankers and a couple defenders, but I was starting to get more into those archetypes right before the announcement...I'd started to figure out how to slot them for a more aggressive, solo playstyle, and was really getting into them. I think that "next year in Jerusalem", I'll probably play my defenders a lot more. Ditto with my Corruptors (who I never got to 50.)
One blaster, one controller...too squishy and too slow for me, respectively, but I'm sure there are plenty who would disagree.
One stalker...too easy, really. You can ghost everything you don't want to bother with. It always felt like cheating to me.
No dominators. To me, they always seemed like the worst elements of controllers and blasters combined. But again, I'm sure there are plenty who would disagree.
No epics, but I loved them. There was just never enough time.