Hmm, Psionics would be pretty fun, I haven't checked up on the powers last, but i'm pretty sure it has like mind reading, and some telekinesis powers.
As for toa tool, I would probably go with some sort of blade, but in addition a projectile weapon, such as a bow, which could be silent.
Mask is a tough one. the mahiki would be a great one to have, as you could shapeshift, and confuse enemies.
Honestly my toa is sounding pretty cool