My favorite was definitely the Toa Metru canister design. The lid was quite easily the best BIONICLE canister lid ever made, and the canister itself was compact and utilitarian. Shame that it was one of the few canister designs they didn't really reuse.My least favorite, if I think of them all as canisters, was the Toa Mahri box thing. Its rim was acceptable as a piece to build with, but... not a canister, really.~ ~