Godot... Because I tried unity twice and hated it. And prefer having an engine than going from scratch especially with short project times
I used the L枚ve2D engine ( L枚ve2D ). I previsouly made some game prototypes with it, and i can say, it's very close to writing the game in c++ (opengl) without all of the annoying stuff. it teaches you a lot about maths for games and it's actually quite low-level so you can optimize as much as you want (obviously, for a jam, that's out of question :D )