Being someone who has a habit of leaving watches places and breaking them, I've always bought the cheapest watches. Of these, I find very cheap Casio or similar to be the most resilient. I've had more expensive chunky sports watches (Timex one, a Casio one), and whilst they may resist more bashing, they get bashed way more, so die easier.
Last watch was a £5 one from argos, which I unfortunately left at the bottom of a whitewater river (was filming video whilst swimming and had the strap caught up in the camera strap – one hectic bit of rapids later, I had no watch). I replaced it with a very similar one from Walmart.
Get one that is '50m waterproof' so you can wear it in the rain (or forget and wear it in the shower) – splashproof ones die.
You can get a fancy £500 mechanical watch, but it won't tell the time as well, and when you drop it in a river, it is £500 down the drain, rather than a fiver.
Joe