Quick rec:
A Battle, A War, Growing Up by
visibleficX-Men: First Class | R (mostly for sex and language, but see warnings) | Darwin/Alex | Author's summary: "Darwin/Alex roadtrip, featuring: angst, self-hatred, sweetness, literary allusions, poetry, boys circling each other and being tentative, a hopeful ending made sad in light of how the movie goes, some geographic fuckery in order to indulge my highway fangirling, and more!"
I'm mostly done with this fandom, but I make an exception for my under-appreciated OTP, especially when it's in-universe, angsty, sexy, and in-character. Oh, my boys.
Hmm, some day I'm going to have to compile a list of my favorite Darwin/Alex stories. Unfortunately, I suck at remembering what I've read.