Here’s a weird one I had a half-baked idea for: Tower Defense Metroidvania. The idea is that your an acolyte of a temple (or a mechanic in a space station, whatever), and there’s an armed group trying to force their way past the temple’s traps and defenses to get to the heart of the temple and steal the macguffin; that’s going on in a little horizontal track at the top of the screen, and meanwhile the rest of the screen is Metroidvania gameplay as you navigate the interior of the temple (or space station) to activate defenses, acquire magical relics, and eventually awaken the temple’s guardian spirit. You lose if the bad guys get to the heart of the temple, you win when you successfully gather everything you need to awaken the guardian. In the meantime, you have to decide when and where to spend resources (including time) shoring up the “normal” defenses (that delay the attackers) and when you need to just push onward to awaken the guardian.