I had a poll on this topic recently, but I'll go ahead and tell you what my favorite features are.
First and foremost, I want QUALITY glass and construction. I guess that pretty much sums it all up, but there are a few other things too.
I also like scopes with Illuminated reticles, I love the rainguard feature, and I only buy, and use, variable power scopes. I am one of those people that tend to buy scopes with 50mm objectives and higher then normal magnifications (i.e. higher than 3x-9x - like up to 12x or 16x or, like my Nightforce NXS scope - 22x). To me, I have no problem shooting a deer at 100 yards when the scope is on 10x or even 14x. Yes, I can shoot it as low as 4x I guess, but I don't have a problem.
Now, let me emphasis that I always start out at the lowest possible setting that has the widest FOV. Then, if there is no other animal around the targeted animal, THEN, and only then, will I crank up the magnification.
Oh, I am also a nut for long eye relief scopes. I don't care too much for Leupold Vari-X IIIs (even though I own a couple), but there is no denying that they have the best eye relief.
Zachary