A fuji 645 rangefinder is in the ballpark on price.....if you want 35mm, Olypmus is nice because it is really compact. Canon EOS is nice if part of what you want is speed of shooting. Honestly, there are no bad systems among the major makers particularly if you stick to prime lenses. The ergonomics of Canon EOS and Olympus OM work well for me.
Canon FD system, for sure. Good glass, good bodies... Get an AE-1P or an A-1. I think the A-1 has more options for automatic exposure, but if you're going manual shutter and manual aperture they are mostly the same. The AE-1P has a slightly better "feel" to the shutter dial so you can bracket or adjust on the flight with a mini-flick of the finger,
All you really need is the body and a 50mm. I would suggest a 28mm or wide of some sort. Then also perhaps a zoom or telephoto depending on your tastes. The good news is you can probably get the camera in perfect condition, and 3 lenses plus more kit all under $400 (your budget).
Compared to larger formats, 35mm is relatively cheap.
EDIT: P.S. I find myself using my 35-70mm f/2.8 zoom more often lately. It's nice for framing shots better. I would recommend something like this unless you have a dislike for zooms in general.
If you need to do fast work the 35mm is the ticket. You know the MF excels in portraits and you can change out film loaded backs between color and B&W. CGW puts the finger on it with Nikon for flash but I'm sure Canon can be good; Maybe Minolta's got them both beat? The only thing I would do is steer clear of the Nikon 50 1.8 D and instead buy the older "N" model with better build and AFAIC better quality control.
Truthfully Nikon lost my business when they pulled the old bs buy it now and buy it tomorrow up-grade game. Examples are the 8008, N80, N90 and F4 where they almost immediately succeeded each with the new "S" version or just super-seceded the model altogether, (N80), hop scotching to the newest/greatest with better matrix exposure and tanking the model for people that just bought it; I believe in the same year if I remember right? Then they used crappy plastic that can get sticky which has affected models F100 and down. Where's the beef in the line? Probably the F5, F6 and FM3A at a price. I have no knowledge of the F3 for flash and the F4 is suppose to be a brick.
I am not sure what to say concerning CGW's comments about the Nikon F and F2. NikonJohn has been using mainly Nikon F and F2, usually with a motor drive, for many years now. My own Nikon F and F2 cameras are still going, although I admit that I do not have anything later than an F2AS. Finding someone to service a Nikon F or F2 is still an easy task. There are many older Nikon users who feel that the hand assembled Nikon F and F2 are still the best SLR cameras that Nippon Kogaku K. K. ever produced. I like the F2.
Then there are the Minoltas. My SR and SR-T models that have been through a CLA in the last three years are cameras that I depend on. The SR-T 102 is still my favorite in that series. They have not let me down. I admit that my feeling of security is slightly less with the later models with the increasing dependance on electronics; the X-700 (which I love with the MD-1 Motor Drive), X-570, X-370, XD-11, and others in the "X" Series, but I have not had any failures with them, and I have a lot of Minolta camera bodies around here. And, while I do like the Minolta Maxxum/Dynax 9 Auto Focusing Mount 35mm film camera, it and the lenses to go onto it may not be in the price range you suggested.
Others have spoken of the Canon FD mount cameras and their lenses. I do not need to repeat those.
In many ways, with almost any of the bodies in the manually focusing cameras and prime lenses to go on them, you really need to hunt to find a camera system that will not work for you. Try almost any of the recommendations you have here. You will not be disappointed.
Almost everything by a reputable brand is great in terms of both glass and cameras. Nikon, Canon, Olympus, Pentax, Minolta, just to name most of the main ones. I would make the decision based on compatibility. In other words, when you shoot digital, or when you do some day, what system do you use (or will you use)? If Canon, get an EOS film camera. If Nikon, the possibilities are near endless. If another brand (e.g. Pentax), do some research to find out what will be compatible with older film cameras. (I am not sure what is compatible with these other brands.)
I owned some nice EF glasses and became curious to shoot film. So, I decided to buy very simple EOS film camera and the choice fell on EOS 650.
This camera just works.
After a while I became interested on mechanical ones. At first on Lecia M3, but it was too expensive for me to experiment. Finally, to Olympus with holy trinity glasses 35, 85 and 135mm zuikos.
Additionally, a boring 50mm zuiko.
Leica R4s and some "BGN" glass from KEH would do it.