Mine is easily the Bombs, Ahoy feat from the Titans alert. I think what I loved most is that it brought back memories of the games from the early years. Everyone moving together with one purpose. The pacing, the traps, the robots. Forced us to examine all of the rooms as we went along, no one running ahead and gave us a bit of story, when you come across Terra, that you would otherwise miss. Anyways, that's my favorite. What's yours?
My favorite is Leader of the Pride, the one you get from keeping all the cubs alive in the catwoman solo
Taking nostalgia out of the mix (as some feats were awesome or quite an accomplishment at level) really any that take some co-ordination and team effort, especially ones that don't revolve around 'moar burn!'. Feats like EO in Paradox, while daunting when we were at level are soloable now. Yeah, back in the day it was one of the best of the game requiring a total team effort to get done, but at the core it's just 'moar burn!', like speed feats or hard knocks feats. In the end those end up being 'give away' feats as stronger groups, even uncoordinated ones, can get them done. I don't care how much burn you have, you can't get AnB '4 corners' without at least 5 people working on it in unison. I've always enjoyed the game most when people are forced to act as a group vs just doing smash and burn runs. Conversely I hate any feats where 1 person can purposely screw it up. Feats like the memory room in FOA recently, or 'One piece' in LnW. One hater can dump it just by touching a button or throwing a shot. Unfortunately there are a ton of these feats in the game.