Film EOS prices are rock bottom. It's a great time to buy.
And as there is no great difference between anything below the top tier there is no excuse not to buy the most recent you can (not to mention less wear and tear, more shutter life etc)
Avoid avoid avoid at all costs:
anything pre E-TTL. This means look for a EOS 300. EOS 30. EOS 3. EOS1V (or the more recent versions therof)
In fact if you get a 300x or 30v you will actually get E-TTL II which will work with select recent lenses to give you even better flash results.
Anything prior to E-TTL (EOS 1n, EOS 5 / A2e, 620 etc) will only work with your flash in A-TTL mode, which is prehistoric off the film metering as it exposes. E-TTL is preflash metered off the subject and far superior.
I currently have the EOS 3, though I recently had an EOS 300x. I would say get a AA grip for any film EOS you buy, the exact model required will depend on the model of EOS you go for, but as photographic Litihium batteries become more expensive and difficult to find a grip will be very useful. I have a PB-E1 on my EOS 3 which also gives it a little speed boost. The PB-E2 is worth the extra if you get a 3 as it perfectly mirrors the controls of the 3 / 1V.
As with any EOS camera I would recommend seeking out one with a pentaprism as opposed to a pentamirror.
This rules out most low end very cheap plastic bodies, but makes the 30, 33, 3 and 1V a good choice. Pentamirrors are crap enough on rebels, but dreadful on full frame.
The 3 is laid out like a current 1 series. Very intuitive to use after a wee leaning curve, the eye control is superlative (in my opinion) and you get AF at f8 etc. It does 99.9 of what the 1V can do (slightly less viewfinder coverage, no viewfinder blind, no EOS link, plastic outer casing but still weatherproof and plenty tough) but adds ECF and is around a third of the price. This also makes it a lot more expensive than very decent midrange bodies like the 30's (a 30v would be my midrange pick)
One caveat with almost all EOS bodies. Most of them use an IR frame counter for film advance and rewind. This fogs IR film. If you are using IR film you may want to look elsewhere or pay the extra for the 1V (there are other IR compatable EOS film bodies, but all pre-E-TTL)
Good luck from a very happy 3 user!
Reala 100. Nice for skin tones. Fairly readily available.
Ilford XP2 Super. ISO400 Chromagenic film (black and white, but can be processed in a colour lab, so 1hr negs / tinged prints possible. Very nice grain structure. Works great with yellow or orange filter to boost contrast a little.
Reala 800. Your low light friend. Go much faster than this and things get really quite grainy.
Velvia 50. Saturated fine grain transparancy film. Use with a polariser. Beautiful. It's like the colour is turned up to 11. Not to everybodies taste, and not for portraiture, but a film you have to try at least once.
others that may be trickier to get:
Fuji 160S really nice portrait film
Agfa Scala (probably impossible, as is processing) a brilliant black and white transparancy film.
Kodakrome 64 (again probably impossible, I've heard of some companies doing very limited batches of processing, a lovely film but probably not worth the hassle)