Again, I am a mosly a Palma shooter, so I use iron sights, but am just saying what I see.
Eric is correct the Nightforce is extreemly popular, next are the Leopolds, then a few T series Weavers.
An entry level scope I see on the line is the Super Sniper. They are inexpensive, have very good optics, are rugged and waterproof. Cost about $300. But, they sure ain't a Nightforce.