Excellent suggestions by fdigital. You can't really go wrong with either an Olympus OM2n or Nikon FM2n. But look at it as a system: how much are you willing to spend on the camera and lenses, maybe a flash as well? Also, check out prices on second hand lenses in the focal lengths you would like to buy. A quick check on keh.com gives very similar prices for Olympus and Nikon lenses like 24mm f/2.8, 35mm f/2 or 50mm f/1.8. I'm stating these lenses as an example of course, they would be my choice for a camera kit, but your preferences may be totally different.
If you find your choice of lenses in both systems, then try to handle each camera. A good photography store that stocks second hand equipment should have these cameras or similar equipment. I started out with Olympus, but somehow preferred the Nikon layout and ergonomics, so changed over and have used Nikon exclusively for the past 25 years.
One thing to consider is that Nikon still makes lenses for the F mount (if you disregard the recent DX optics made specifically for smaller digital sensors and also the G optics which lack an aperture ring). Olympus have been totally out of the film SLR business for quite some years now. All things considered, I think you'll have a wider choice with Nikon, but then again, I'm not that familiar with Olympus. The bottomline is: check prices, compare and make an informed choice. Once you commit to a system, any change is going to be expensive.
