Unno, for a keychain light, bouncing around in a pocket with other crap that can press in random places, I’d prefer a twisty to try to prevent accidental activation. So for me, a Jet-II would be about perfect for a 16340 light.
Some of the Wuben E-series come in 16340s as well as 14500s, so czech ’em out, too.
Funny(?), but every time I see your handle, I read it as “Mr Steal Your Organs”. Visions of waking up in a bathtub filled with ice are rather disturbing, I gotta admit.