Full disclosure: I have nostalgia-goggles for this.

Early-era sidescrolling that switches in to NSEW 1st person room searching for portals in to other worlds where you're back in side scrolling. The mechanics of this game are rough but the tone is wonderful 80's camp and it awoke something inside me as a kid. Intro'd me to a lot of horror cliches (zombies, flying skulls, body horror).

If you don't play it, at least take a look thru the spritesheets for some sensible chuckles.