I would go for a Omega or Rolex (second hand?). Maybe boring. Or you know what? What about a Sarpaneva K0? That would make a very cool beater would it not?
Personally I have changed my mind about daily beater watches.
At the moment I'm using my most valuable (as in loved & $$$$$) watch as my daily beater. It's my PP 5980-1A. I used to baby it much more but at some point I figured that it would hardly get wrist time that way. And why pay a lot of money for your most wanted (ex-grail) watch if you keep it in the safe all of the time because you worry about scratches and so on. NO MORE I thought. So the Nautilus is living a life now and it shows. And because of that I am wearing it 90% of the time.
It's out there and I'm loving every minute of it (think Kramer - Seinfeld).
Scratches=Character