Lucimarth 1123 and 3123 for reasons PKL stated. Sometimes I go 1123 because shield breaker can be clutch.
Mario 2312. I find Fast Fireballs much better than default and Fire Orb. Gust Cape to push opponents away from the stage.
Shulk 1113. Power Counter can kill so early.
Sheik 2211. Penetrating Needles charge up way faster and does good shield damage. Gravity grenade can be pretty fun if you land it.
Palutena 2312. Super Speed and Lightweight make palutena so much fun to use. great combos and explosive flame for being unblockable last hit.
Mega Man 3323 and Toon Link 2131 for Reason stated by Jedi and PKL.
The rest of my Mains I stick to default. (ZSS, Sonic, Robin, Fox, Falcon, and Diddy)
I might try Thunder+ for Robin though. How is it?