I use a Paterson Triple Timer -http://www.patersonphotographic.com/patersondarkroom-details2.htm#middle

It makes a Bleeping noise as each of the time periods are up.

I set the first time for Developer, the second for Stop and the Third for Fixing

As all 3 timers run concurrently, it allows you to time the whole process in one easy sequence.

There is no back-lighting - so great for complete darkness.

The only additional feature I would like the timer to have would be it made some sort of "tick-tock" noise to show it is running.
I find standing in the complete dark, time seems to be a strangely elastic sort of thing - sometimes my 8m15s Dev time seems to be unexpectedly short catching me unawares and yet for others it is an absolute eternity – making me wonder if I have set the timer running.