In the right genre setting you can survive with surprisingly little of your body intact. Science fiction of the cyborg variety can effectively stick your head onto a robot body so you can get around, and even potentially be stronger and better equipped than a normal person. The weird science category can stick your disembodied brain into a jar and have you control an empire. And then there's magic, of course, which can sustain nothing more than your empty skull as a viable ongoing character.

Naturally, this doesn't just have to apply to PCs. Consider making villains and adversaries slightly less than whole physically. Of course they'll get to compensate in various ways...

Transcript

Jabba: As you know, Han Solo had many enemies. None so wealthy as myself, so none willing to pay a lot for him.
Jabba: But many willing to pay a bit. So, to maximise profit, I'm selling bits of him.
Boba Fett: Don't forget, I have rights to a scan of every brain slice. Obi-Wan Kenobi shall be mine.
Jabba: Yes, that's no skin off my nose.
Boba Fett: Well, obviously.
Jabba: Mmm.
Leia: Kee ato cha.
C-3PO: "No, you're not cutting him up. I'm buying all of him."
Jabba: Ha ha ha ha ha!
Salacious Crumb: Ha ha ha ha ha!
Salacious Crumb: Wait, I don't get it.
Jabba: You can't afford him. Even that holovid could buy at most 15,000 slices.
Han: That's pretty good!
Jabba: Which is 8% of him.
Han: Hmmm. Which 8% are we talking about here?