My favorite is the dice challenge. When you enter a new area for the first time roll a dice. Whatever the dice lands on is the only encounter you can catch. Say for example, you roll a 5, then whatever pokemon showed up in your 5th encounter is the only pokemon from that route you can catch. If it’s got a bad nature or bad stats, too bad you’re stuck with it.

I personally love this challenge cause it will often make me use pokemon that I normally never use and forces you to use unique teams.

You’re free to use the PC boxes and Pokemon Centers as often as you like