I'm a fan of military surplus firearms, mostly because I'm a college student and just can't afford much, yet I'd still like a fairly robust and reliable firearm. Additionally, I enjoy target shooting and plinking and surplus ammunition makes that affordable.
For that reason, I tend to prefer them when considering firearms to carry for hunting / survival, but of course other rifles (like lever action, etc) would certainly do.
A shotgun or .22 would probably put the most food on the table at the end of the day.
For medium sized game out to 200 yards or so, just about any intermediate powered round would do... it comes down to how handy the firearm is.
At that range optics may not be necessary, but I still like them. So long as there are iron sight backups immediately available, I'm not too worried about durability in a survival scenario.
If money were no object (yeah right!) and I wanted a firearm to take small game, I would be happy with a PS90 in short barreled configuration. You have a very compact and handy firearm firing ammunition in the same class as .22 magnum, so coyote / hog / deer sized targets are plausible in a pinch. Has an optic as well as iron sight backups. Include a flashlight to help locate smaller game in twilight or darkness. I like semi-automatic, and 50 rounds in a magazine simply means I can leave it in there and don't have to worry about it for the duration (bringing a spare of course should magazine issues occur).
Then again... I suppose a 10/22 or AR-7 could do 90% of that at 1/8th the cost