So this thread is for the discussion of interesting variations on standard Pokémon game playthroughs. Most people seem to play through a Pokémon game and raise somewhere between 1 and 6 Pokémon, which they level at roughly the same pace up through the Elite Four. I'm a huge Pokémon fan, and I've played every Pokémon game (in the main series) through at least once in that manner (every game from RBY through W/B2W2). 

What I'm looking for is a way to get some replay value out of my games by playing through them again, but I don't want to just play the standard way. I want some added challenge. I know B2/W2 have "Challenge Mode", and I've played through on that mode as well.

Variations I know about already:
Nuzlocke: If you don't know what this is, Google is your friend. I won't sit and explain it here.
Monotype: This is playing through a Pokémon version (any version) whilst only catching Pokémon of a given type. My personal favorite is Water-type in Third Generation.
Solo Run: This is actually easier than the standard (raise 6 at even levels) approach. I'm not a fan.

These are the only variations I can think of. Does anyone else know of other variations and/or can anyone else make one up?

EDIT: To the mods - I'm sorry about using the Pokémon subforum. I hadn't read the sticky until just after I made this thread. My bad.

BenTover : You can do a gym leader run, only using the pokemon from one gym leader. I did sabrina in crystal, winona in emerald, and morty in soul silver. I use there teams from the rematches, except sabrina
The run is fun and you can really get screwed when you fight like a dark gym leader with sabrina's team.
I would check it out.

You do need a wild pokemon modifier cheat code but other then that youre good to go!

I do the runs where i catch as many Pokemon as possible and level them all up the best i can before the Elite Four, I don't just stick to the standard 6 Pokemon.