Great for the $$$ - NcSTAR Red Dot Sight - 1x30 B-Style Red Dot - 3 / 8" DBB130-3

Tried this out on a S&W MP15 and was pretty happy with it; I was hitting an 10-in. target that I could barely see at 220 yds. Sight was still dead-on zero after about 100 rds. of 5.56 - I'll have to see how it holds after a few hundred more. Also, it mounts very low and if you want it to co-witness with your BUS you will need a riser; I used the NCSTAR quick release and it's a slick little setup for under 100 bucks.
If you're jumping out of helicopters, get an Eotech. If you're shooting old washing machines in the back forty, get one of these and spend the rest on a big ole can of ammo.
Pros: Cheap. Stays zeroed, so far.
Cons: Won't co-witness, eats batteries.

This review was written in the old system and had content requirements that are different than reviews written today.