Oh there's piles of one & done games out there- my personal soft spot is for Cyborg Justice, a decent enough side scrolling beat 'em up with the interesting gimmick of building a custom cyborg prior to the game's start, then modifying it on the fly by literally ripping your opponents apart & taking their parts. Decide partway through a level the flamethrower arm is better than the chainsaw arm? Pull it off another guy & put it on yourself. Just keep in mind taking an arm won't kill him & he can still try to kick you to death. (You can also take legs & torsos. That'll kill 'em.)
I tend to be more interested in games that managed multiple releases, and yet have faded from the current scene completely. I'm sure you can guess one I'm into *points to avatar*, but another favorite is Lunar. Especially Lunar the Sliver Star- it amazes me how a game can stay so firmly in the 'niche JRPG' category when it's managed to get SIX friggin' remakes in! Especially since all of those happened well before the 'X game remastered edition' craze really kicked in. Somebody out there must've really, really liked this story to keep pushing it.