I know that this is not the popular choice. Most people want something newer or more technologically advanced, but I actually prefer the SKS as a field rifle. I have owned a ton of rifles and have plenty in the cabinet now and been shooting since i was a tiny kid. I went through the phase before my 20's when I wanted to put together a ton of "black" rifles and thought that all of the high end stuff was really cool like HK91's and M4's, etc. Through the years I became less and less impressed with all of that stuff and started noticing that the more dependable and simple a rifle was while still maintaining accuracy and reasonable cost, the more I steered towards it when I would choose a rifle to run off into the woods with. Keeping AR's, Hk's, and all those others clean and feeding with no problems was a constant thing when you add the elements and shooting grime. Another rifle i tried while looking for the best "field rifle" was an AK. Unfotunately you can't hit the broad side of a barn with one from more than 100 yards away. They're the most dependable rifle on the planet, but they're just not accurate enough and if you find a really good one, you're already back up into the higher price range. I've owned somewhere in the neighborhood of 30-40 SKS's of all different sorts and grades and found that they were the perfect mixture for me of dependable, accurate, reasonably priced rifles. Now keep in mind, you don't just want to grab any old SKS and use it as an all the time field rifle. You have to take your time and choose one. It's best to get one of, what used to be known as, the usual SKS's in good condition. What you want to stay away from are the Yugo's and nasty user grade models. They won't have some of the finer points that make SKS's great like chrome in the barrel. They also come with useless things you don't need like grenade launchers and they weigh a ton more than good SKS's. I know it's hard to see what you're getting under all of the cosmoline, but if you know what you're looking for, you can find a good one fairly easily. Some of the things you want to look for are:
Try to find one without too many bangs on the stock and the least markings possible.
If you can find one that is a "factory 26", you'll be able to tell by the pyramid shaped cartusche on the reciever will have a 26 in it, get one of those. I've had the best luck with them.
Check the bolt and make sure that it works very well and locks all the way forward with no hangups. I've had a couple of SKS's that had a slight hangup where the gas port blows the rod throught the hole to cycle the weapon and it missed regularly.
Try to find one with the cleaning equipment still in the gun. This includes the cleaning rod under the barrel and the cleaning kit in the stock. To check for that, just push on the circle in the butt of the stock and it should pop out. You'll have to press pretty far, but don't get your finger stuck.
A couple of rare models to look for are the paratrooper model and the "D" model. If you can find either or those at a good price, they're terrific. The paratrooper is a little more compact, but still extremly accurate with practice and it will save you some space on your person. The "D" model accepts AK mags and are of unusual good quality.
Now that I've been going on forever about these, you get my point. I like them a lot. You can pick up most of them for about $100 a piece and they are EXCELLENT field rifles. I have yet to have one of my good ones jam or lose accuracy from any conditions, including being covered in mud and sand. Great guns. I carry either an old Norinko Chinese model or a Soviet paratrooper with me anytime I "get lost".