There are a couple of things you need to settle first. One, this totally depends on what you mean by "classic style." Two, you need to decide if you want an automatic or a quartz watch. Three, you need to settle on what exactly you mean by "tough."
The quintessential "classic style and tough" watch is a Rolex. They are more-or-less indestructible and many Rolex owners wear their watches every day for decades. Most Rolexes are designed for diving, and the Explorer model, for example, was the watch Sir Edmund Hilary when mankind first reached the peak of Mount Everest. They are definitely classic and definitely tough. They use a type of steel that is very expensive and much harder than ordinary stainless steel, which is part of why they cost so much, although you are definitely paying for the name, as well. Rolexes require regular maintenance and are not as accurate as quartz watches. A used one can be had for under $2k if you know where to look. They are not as accurate (as in takes a licking and keeps on ticking) as some other modern diving watches, considering that they are automatics - if you want reliability and accuracy under any conditions, consider a more modern dive watch.
Omegas are also good watches (for example, the Seamaster Professional). Both are automatic watches, which means that while they don't require batteries (they run on the power from the movement of your wrist), they are also not as accurate as quartz watches. It's an irony of the watch world that the more expensive watches are actually less accurate and (usually) less tough than the cheaper ones - a $200 Casio G-Shock can take a lot more abuse than a $5,000 Rolex and keep better time doing it.
I'm not a digital-watch fan, unless it's truly for sport (like a watch for timing yourself while running or something), in which case I would recommend a $50 Timex. It's like driving a sportscar with an automatic transmission - if you're going to get a nice watch, get an automatic.
For something that's really tough but not $2,000, you might check out Reactor watches. Along with Casio G-Shocks, a lot of military guys wear them. They are extremely well-made and a good value. You can get them for around $500, and another nice thing is that many of their models have tritium hands & hour markers. Tritium is a gas that is slightly radioactive (don't worry, it's perfectly safe) that glows all the time for about 10 years until the radioactivity decays. Watchmakers put this gas in little tiny tubes and affix them to the hands & hour markers. Unlike glow-in-the-dark hands & hour markers, you don't have to "charge" tritium with a light source before it will glow; it's "always on" - it will be just as bright at 11 PM as it will be if you wake up at 4 AM and glance at it on your bedside table. One of my regular watches is tritium and I especially like it for going out on the town or for driving at night. It's a Traser H3 (what the US military issues), not a terribly expensive watch (~$125), but it's tough and works just fine, and keeps time better than many other watches.
I would recommend a Swiss-made watch. The Swiss know what they're doing when it comes to watches and most of the best watches in the world come from Switzerland. Traser is a Swiss brand, so are Rolex and Omega. Another good brand to check out is Victorinox. That is what the Swiss military issues and they're in your price range.
If your dad is accident-prone, make sure to get a watch with a (synthetic) sapphire crystal. Almost all watches $300 and up will have them, but you should double-check to make sure. Sapphire crystals are very difficult to scratch, compared to mineral crystals (what most cheaper watches have).
World of Watches and Amazon are both good places to buy a watch. Both have good return policies so you can try them out and see what they look like in person. I also recommend checking out the WatchuSeek forum - lots of good information there, and they have a for-sale classifieds section if you're interested in a used watch. There are LOTS of watch collectors there who go through watches like candy, and you can often pick up a great deal on a used watch that's either brand new or almost brand new. You don't get a warranty or a return policy if you do this, but you can often get 30% or more off the cost of the same watch new, if you want to really make your $500 go as far as possible. I'd say that $500 is just starting to get into really decent watch territory.
Hope this helps!
- Dave