8: Favorite all time stage?
I tend to have a fondness for the more gimmicky stages that most people don't seem to like. Stuff like the Ice Climbers stage from Melee, Poke-Floats, Pictochat, that sort of thing. They're not very good for more competitive play, obviously, but they're clever ideas and they tend to stick in my mind a lot more than some other stages, which are nice, but just sort of plain. Like, I remember the Bulbin in the Pikmin stage because it walks up and can eat players, but the rest of the stage is mostly plain.
Ironically enough, despite that entire paragraph, Fountain of Dreams is my favorite Smash stage. It doesn't have many quirks, but it's got a fantastic design and one of the best damn remixes the series ever produced.
The Luigi Kick™. I imagine a lot of people like that one. I also like Mario's Super Mushroom animation taunt.
23: Play with or without items?
I used to be very heavily on the 'with' side of things, but a couple years after Brawl was released I started to mellow out. Nowadays I don't really care; the items can help make things a bit more randomized, which is fun in its own way, and having them off makes gameplay more fluid, which is also fun in its own way.
What matters more to me is whether cheap tactics are used or not. I'm all for fighting dirty when the ability is there, but I had one match once where the opponent was Kirby, I was Marth, we were on Final Destination and time was running out, and Kirby decides to float to the top of the map the last few seconds so I couldn't reach him. I can't even respect a stunt like that, it's not fun for either party.