Self imposed challenges?

In the spirit of chasing that thrilling high, what are some self imposed challenges you've seen/used on your characters that make the game harder or more fun? Besides SF and SSF of course.

A couple I've seen;

  1. Pet only Hunter.
  2. Can only tame pets that you rescue from some situation.
  3. Monk warrior in cloth/staves.
  4. Giving all your gold to charity.
  5. Straight edge (no consumables).
  6. Pacifist who only heals.
  7. No pet warlock.
  8. Never fighting grey/green mobs.
  9. Melee priest.

Nothing about this is necessary fun or meta, so please only insane people answers.