that's a really broad question. it would be helpful if you would narrow it down a bit. There are lots of good companies out there. Things that might make it helpful are your parameters...price, magnification, preferred companies etc.
Without knowing any of that, if I could walk into a store and buy the scope I want. It would be a Nightforce 5.5x22x50
5.5-22x50 & 5.5-22x56