A Taser might work but you have to get real close. Besides, one bullet hole is not going to cause rapid decompression of the plane, "Goldfinger" notwithstanding and if you are probably going to die anyway, why not at least have a chance.
Crossbows, etc., have little or no stopping power unless you hit the heart or brain and kill them instantly. The reason a bullet is so effective is NOT because of what it hits (unless it's the heart or brain) but because of hydroststic shock which affects all the organs of the body.
Give the pilots guns say I.

troll