6th pokemon for my team?

I'm playing fire red and have beaten every part of game just looking to really create the best possible line up now before going on a catching spree.

I have the following 5 set:
Charizard - blast burn, flame thrower, dragon claw, rock slide
Mewtwo - Psychic, shadow ball, brick break, and recover
Jolteon - thunder, thunder bolt, dig, bite
kabutops - giga drain, surf, aerial ace, hyper beam
dragonite - fly, ice beam, outrage, earthquake

Im able to go through elite four attacking their weaknesses every time without being vulnerable to a counter super effective attack, so im just looking for a cool, strong pokemon thats different then the others. Thanks in advance :)

Yeah I thought of tyranitar like 5 min after i posted haha getting him set up with earthquake crunch hyperbeam and brickbreaker thanks for the help

I agree, Tyranitar would be a nice choice.