All kinds of things:

Combined with Duct tape a section can be used as a temporary heater/radiator hose patch

Since it is stretchy it can be used anywhere a rubber band can...only bigger

If you have two things touching that should not be touching, stick a chunk of inner tube between them

Those are only the ones that come to mind that I remember using it for.

I used to carry 19" front wheel motorcycle tube on all my motorcycles because in a pinch it could serve front or rear (rears tended to 17") but then I found that more often than not I ended up cutting it up to do things like to tie a saddle bag shut or put between the seat base and the battery post when metal seat pan kept contacting the post.