Are they any others that have a timeout?

The Windows NT boot manager has a timeout, but it's *very* easy to get
it to flake out and not boot NT (just by creating a partition in the
MBR using the NT Disk Manager (or whatever it's called; I'm *not*
inclined to go look), no less).

I wasn't able to get it to boot NetBSD, either, but I didn't try very
hard.