Basically any upbeat song that reminds you to appreciate life in the middle of absorbing and applying theory. Anything from the Internationale to Red Army tunes to modern(ish) artists like Chumbawamba are allowed. Even Lofi.
Personal favorite of mine is Quand Fera-T-Il Jour, Camarade? by Mireille Mathieu. It's bittersweet, hopeful and resolute. Even if I don't speak French, I sometimes mumble to it.
Runner-up would be Solidarity Forever by Pete Seeger.
Lmao Hakim has a 2 year old comment in that Lofi comments section.
Anyway the song that pumps me up the most is Oh Fields My Fields.
I'm also a huge fan of this Swedish song about Vietnam but it might not fit the bill for this thread. It does teach basic theory though.