A sniper rifle is a specialized weapon, and normally pretty useless for anything else than its designated purpose. An accurate semi-auto battle rifle or carbine would be a better all-round weapon. Something like a PTR-91 (one of my favorite .308 rifles) or a FAL will hit hard and accurately at long range, but can still be used for CQB. The PTR is a heavy SOB, but if you know how to shoot you can consistently hit a man sized target at 200-300 yards without even using a scope. If you want to use a scope and go out further, you will need to learn a lot about how temperature, wind and other factors affect the bullet, figure out the best load for the gun, practice a lot, keep a log etc. If I had to take a wild guess, this is not really what you have in mind.
The PTR-91 (Precision Target Rifle) looks more impressive than the other suggestions that are really legal, but would it be my best choice.
Time will tell
PTR rifle - Wikipedia