Have you ever tried (and maybe accomplished) clearing the game with a limitation or goal that's not coded into the game?
Basically, have you ever done a self-imposed challenge on a Pokémon game?
We already have a Nuzlocke challenge thread, but the Nuzlocke challenge is an example of this. Speedruns also qualify, I guess...
Other examples are using only Pokémon of one elemental type (a Mono-type run), not evolving your Pokémon, using a team of 6 equal Pokémon, using only one Pokémon, defeating legendaries or strong trainers or Pokémon with Level 1 Pokémon (I've seen a video of someone defeating Cynthia in B/W using a team of Level 1 Pokémon... well, they started at level 1, but then they leveled up during the run. Still counts),
Also particularly interesting is the Christian Playthrough I found on TvTropes.org:
No evolving your pokemon
No dark, Psychic, or Ghost pokemon/moves
No Ekans, Arbok, Seviper, or Serperior
Pokemon must be LV 22 before they can breed
Pokemon of the same gender can not share a daycare center
It is your duty to keep any egg pokemon in the party til LV 18
Legendaries are false idols, and should be killed
Cant use Fossils, Game corners, or drugs (PP Up, Rare Candy, etc)
I'm currently doing a Rattata-only run, using only a single Rattata to clear Fire Red. Let's see how far I can get!