Every great rifle needs some great glass. You could drop $100 on a scope for your M82A1 Barrett but we expect that you wouldn't be able to hit the side of Mount Rushmore from a hundred yards (probably not true, we know your shooting skills are on point). A recent rule of thumb is purchase an optic within your maximum price range that has the features required for the purpose of your rifle; see below for our recommendations.
For rifles such as AR-15's, you cannot go wrong with EOTech, Trijicon or Aimpoint; they are the go to brands for a great price to quality ratio. EOTech offers great optics such as the EXPS3-2 Holographic Sight or the Hybrid Sight II. From Aimpoint we offer the extremely popular Aimpoint PRO Red Dot sight - it's kind of the be all end all of AR Scopes because of its price and durability. Another great option is the assortment of ACOG Scopes from Trijicon that we offer. You can expect great quality and performance, plus they are sure to be the envy of your gun crowd friends.
Maybe you are needing to go with a little longer range, something of the hunting or competitive long range shooting genre. Check out our Rifle/Shotgun Scope Recommendations category. There truly are too many to list so we just went ahead and built a category around the purpose of your rifle to save you time. Here you can expect to find popular quality brands like Bushnell, Vortex, Nikon and Zeiss.