As said - handgun vs long gun will make a huge difference on recommendations.
For longguns I have a few guns with various types (scopes, traditional notch/post, peep), but I honestly don't shoot them enough to really have a good feel for recommending anything.
For handguns, I know that a lot of people have said that having a fiber-optic dot in their front sight post (but ONLY the front - dots on the rears tend to draw away your focus) tend to help. Something like the Warren Tactical sight sets are taller than many stock setups which I like (more sight to see) and are available with fiber-optic fronts. I still like to run plain black on those, but I'm running Warren sights on both my M&P and my Glock 17 and they are great on both.