HK91/G-3/CETME- Nice rifles. Accurate, reliable, but a bit heavy; a real handful. Not a huge fan of the action, as it gets very dirty; field stripping is a breeze but don't lose those pins. Stamped receiver gives me pause; if you were to impct it on a hard object (rock, vehicle, etc) would it dent and cause problems? Mags are dirt cheap and parts are plentiful.
M-14/M1A- A fine target rifle. As accurate as they come. Proven Garand type action. A bit heavy, and the traditional stock doesn't allow for Assault type carry, but a good gun, if expensive. Reliability is excellent, and this would be my choice for long range work. Parts are plentiful, but mags are expensive because of the next rifle in our list...
AR-10- Haven't fired one, but I've seen them work at the range. Outstanding accuracy, I'm told fine reliability, handles well, but expensive. Parts aren't plentiful, and mags are pretty expensive (they use M-14 mags, and Armalite's decision to do this has driven up the price of M-14 USGI mags to about $50 a pop. The AR-10 is a fine gun, and if not for politics, the US probably would have built it over the M-14 and M-48 (FAL).
FAL/L1A1- Ahh, the right arm of the world. The West's answer to the AK. Again, if not for the "It ain't made here" mentality of McNamera and his "whiz kids", we, like 80+ other nations would have adopted the FAL instead of the M-14. Accurate, reliable, easy to maintain, pretty damn good. The downside? Well, they are a bit heavy, and somewhat over-long. But they are simple to fieldstrip, in my experience, stone reliable, and parts and cheap mags and accessories abound. My STG-58 is as accurate a gun as I own. While not quite match grade, it will give stock M1A's a run for their money with Portuguese ammo. If I had to pick one, I'd pick my STG-58, but there's an Israeli clone on the way, with an 18" barrel that might be a bit more handy, so I'll reserve judgement for about a week or two.