Aimpoint for a Red Dot. If you're looking for magnification, the NightForce NXS compact series has proven to be a good choice. I've been using a 1-4 on my 3 gun rifle for about four years, and have had zero issues. I've been able to reliably and consistently hit targets from point blank to 600 yards.
The Vortex scopes have a good reputation as well, I just have not been able to play with one personally.