I often follow the below process when deciding on what I should do.
- I should do $X.
- Hmm. $X is either:
- What everyone does ("It's too obvious").
- Something I have already done at least once ("Too boring").
- Not a challenge.
- Eventually: I'll do this crazy thing with some minor elements of $X added in here and there
It usually ends up working out quite well, though, so I'm happy with this process.