Another vote for Aimpoint. Any of the micro models. H-1, H-2, T-1, T-2. Or the Comp series [M4, M5 etc...] I've owned a handful over the years. They're actually not even all that refined. lol. Most Holosun's will even have a more perfect looking dot. But they will take serious abuse and last forever. They have the best track record of all the red dots. That's why I trust them.
If wanting to go cheaper then look at nothing less than the Holosun's. They're pretty good for the money... They may even be as good as the Aimpoints, but they don't have a long enough track record to show it.