Lots of good ones out there. Red dots are fast, fast, fast - I've used Aimpoint and Eotech on long arms and have a Burris Fastfire on a certain pistol that of course I never shoot because shooting is noisy and dangerous. The problem with a reflex sight is that the 4 MOA dot that's so fast under 50 yards covers a 12-inch area at 300. Crank that down to 1 MOA for distance and it isn't quite as easy to pick up close in. Tools for jobs.
Don't forget your irons. Glass breaks, batteries die, but if you have flip-up irons you're still good to go.