Too many different kinds of watches to really give a straight answer.
For a classic dive watch - Rolex Submariner, Rolex Sea Dweller, or Omega Seamaster
For a chronograph - Omega Speedmaster (Rolex Daytona is out of your price range but I still prefer the Omega on aesthetics and legacy)
For a pilots watch - Breitling Navitimer, Oris Big Pilot, or a nice Laco (I have a Laco Faro 42mm and it's a great watch)
For classic styling - Rolex Milgauss, Air King, or Oyster Perpetual, a nice IWC, Nomos Glashutte, or a used Patek Phillipe. I am in love with the 70th Anniversary addition of the Omega Seamaster 1948 Vintage Small Seconds version.
It's hard to go wrong with a Patek, AP, Rolex, Omega, Breitling, Tag, or IWC. Don't be afraid of used with these brands as they'll appreciate over time if you take care of them.