The Ultimate Multi-Type Challenge!
Basically this: You have to beat the game with all of your Pokemon being dual-types and having moves that don't match either type nor each other.
For example, let's say one beat the game with a Venusaur, Charizard, Butterfree, Beedrill, Pidgeot, and Fearow. It would have to be something akin to this:
Venusaur :~: Double-Edge, Earthquake, Rock Smash, Sunnyday
Charizard :~: Dragon Claw, Shadow Claw, Slash, Solar Beam
Butterfree :~: Psybeam, Poison Powder, Stun Spore, Safeguard
Beedrill :~: Rage, Assurance, Agility, Solar Beam
Pidgeot :~: Sand-Attack, Twister, Agility, U-turn
Fearow :~: Assurance, Agility, Drill Run, U-turn
Each of those Pokemon are dual-types. Each of their moves are both different from their user's types, as well as different from each other. It would basically be a challenge to cover many, many more types than usual.
Your thoughts? I may not do it, but I'd find it rather fun :D