The best scope ever : the one you design yourself to fit with how you want it to be.
Good scopes are inobstructive (to keep a view on everything, while you are blind in some parts with standard scopes, for example behind the shooting point with iron sights), allow an easy detection of the shooting point, and give a good accuracy. If you want to design your scope for score, and don't care about its look, that's the way you should design it
For example, the scope I long used for the SMG :
http://www.mediafire.com/i/?bips44viv3ux6o3It tripled my kill ratio, I used the basic iron sights before

The Scarmory : all my mods :
viewtopic.php?f=71&t=6995Mass Effect Pack V.7 Available - scopes (finally) included !
"cease fire, Grenadier ! The Old Guard only fights with the spade"