Mechs vs. Minions is one of the most entertaining board games that's hit my tabletop in some time.
If you haven't heard of it the gist is that four players take control of various characters from the League of Legends franchise and do battle against NPCs with a modular board and evolving missions. It's a co-op joint, and said missions really do evolve in the sense that you're taking on new concepts, and even eventual RPG-like upgrades. The best part of the whole affair is that you're cracking open new boxes with brand new bits and pieces to incorporate, including an eventual giant "warning, do not open" package. It's a wacky game and the over-arching story you're following as you take these scenarios on only adds to it.
The thing is, it's nearly impossible to find, as Riot Games, creator of League, has to reprint it. Well, they just did that and are now offering Wave 3 of Mechs vs. Minions if you've been itching to play it. Note that while $75 is pricey, you're getting a lot in the box. I'd recommend going in on it four ways with friends and committing to the campaign.
Mechs Vs Minions (Wave 3) [Riot Games]