Challenge 10: The Frankengame

This challenge is inspired by a comment made by a game designer I know.
I forgot where he originally posted the idea, otherwise I'd link to it.

Anyway, your challenge is this:
Design a game out of the left over bits you didn't use in other games you made.

As the submissions here are largely thought experiments and not final games that could actually utilize unused art assets, I will modify what I'm asking for a little bit:

Design a game out of game mechanics you devised, but which were ultimately cut from the final design, in at least 2 different games you've worked on in the past.

(But hey, if you want to actually go out and do a digital game using old unused art assets that's fine too!)