The Legend of Zelda Breath of the Wild. Well, I know what my YouTube viewers want, and much of it includes glitches and challenge runs related to that game. Had a fair few popular videos based around stuff there, like a recent one about how to get infinite Korok seeds via a new glitch.

Other than that, Luigi's Mansion 3 (often the online mode), Super Smash Bros Ultimate, and whatever fan games and mods I feel like playing right now.