I want a challenge where I can't basically solo it. Only single types and Normal/Flyings? Solo with Blastoise w/ Pidgeot for backup against Venusaur. GSC? Kadabra/Machoke duo. 3rd gen? A little bit trickier, this would be the most fun. 4th? Main with Staraptor, have a couple of gents for backup (esp for Volkner and Candice). I really liked the Gym Disadvantage one, because you had to keep switching out your team. Make more like this.
Hmm, I don't want to start a challenge, but here's an idea:
"You're an idiot" challenge: You can never, ever, during the course of the game, have a type advantage. This means that your pokemon's type cannot resist the opponent's type, and that your opponent's type cannot be weak to your type. For example:
Say I'm using Voltorb. You cannot use a ground type, as it is resistant, and does good damage against me. You also cannot use grass, because it's resistant against me. This means that nearly every type versus itself is outlawed, with the exception of normal. You'll have to switch your team around based on the trainers and the route. If you have a type advantage, you must immediately switch to a pokemon that does not, or run. If neither option is available, reload from your last save.
... So, anyone masochistic enough to try it?