Yeah I played Broforce local co-op with a friend ~1 year ago and it was amazing!

Bastion is great, too.
Hmm... looks like I'm going for KSP (still unsure, see below) and a donation to URW (wanted to do this ever since I discovered URW). That'd be enough money spent on games for the upcoming month. Okay, I'll probably get Broforce + a copy for a friend (so we can play something else than just Dota) also.
These ain't the ones I initially wanted to get (at least not in November), but hey I think they have most replay value and are among the most playable ones I listed. Afterall, the other games won't vanish from earth.
Thanks for your suggestions!

By the way, anyone remembers those awesome CDs with dozens of demos on it you got with PC magazines? Why are there so few demos nowadays? I think demos are great.
Edit: I've already seen KSP on a few sales on Steam and even the Humble Store. I think I'm just going to wait for a sale there. So... definitely going for Broforce and donation URW. Everything else will be decided spontaneously or next month because I remembered that I'll get a game pad gifted soon that makes a lot of games I already own finally playable.