Another is the Bushnell trs-25 for a short tube type dot sight.
http://www.midwayusa.com/product/593456/bushnell-trophy-trs-25-red-dot-sight-1x-25mm-3-moa-dot-with-integral-weaver-style-mount-matte
I have a Fastfire lll, an older Ultradot, the Bushnell, and an AIM like that Buckmark listed above and they all work well. For more precision shooting, I prefer a smaller dot.
One nice thing about red dot sights is, after zeroing, if you can see the dot that's where the bullet hits. There is no eye relief or parallax problems with them.