Recently I got the idea about making a challenge based on the books of the Gone series. So far there are 5 released books and I've made a ruleset based on each one of them. For an ultimate challenge you can go through all the rulesets on 5 different games!
The challenge rules:
Book 1: Gone
Pokemon that evolve must be released. You cannot hold up an evolution. This means that at level 16 your Charmander will evolve and must be boxed/released. However, if you catch a Raticate it will not evolve anymore so you will be fine. Same with Pokemon that don't evolve or Pokemon with trade or stone evolutions, as long as you don't get the stones.
Book 2: Hunger
You cannot use berries. You cannot use plant or animal like Pokemon, unless they are of the poison type.
Book 3: Lies
You have to use your starter in every Gym Leader or Rival battle and it must defeat at least 1 of the opponents Pokemon. After the fourth gym you have to release your two highest leveled Pokemon, apart from your starter.
Book 4: Plague
You cannot use medicines like Potions or Revives. Pokemon that are affected by a status problem other than Confusion have to be released or boxed, unless you can heal it BEFORE the end of the battle.
Book 5: Fear
You must always have a Pokemon with Flash on you. You must also use a Pokemon hatched from an egg, or a baby Pokemon. (you are allowed to evolve it) You must also use a Ghost or Dark type pokemon.