Favorite: Off the top of my head, I recall the Chun-Li Spirit you fight open first entering the Street Fighter Map being really good. Metal Sonic is a close second, if only because "Holy Crap! They finally acknowledged that Sonic not turning into Metal Sonic when he gets a metal box is a missed opportunity!"
Least Favorite: The WoL match where you fought Incineroar, Villager and The 8-bit Sheriff Assist Trophy on the Gamer Stage was Melee Event Mode levels of unwarranted horse****. May that Event Match rot in a ****ing Landfill Wildfire buried under piles upon piles of molten Atari E.T. Cartridges. Second least favorite was Adam Malcovich, but that's only because they actually bothered to acknowledge that butchered corpse of an assassinated character. I feel infinitely sorry for Snake for having to endure being possessed by that utter embarrassment. Thankfully, the actual fight itself was quick, painless and completely optional.