I bought a Torrey Pines thermal imaging device for night-time work. I'll probably put it on either an AR or a Mini-14. It's good to 100 yards, so the gun doesn't need to be any better than that.
For those of you who can’t afford much, Leapers/UTG has developed their sights into some of the most durable and useful sights (tough construction, good glass for low light, etc.). Their reputation over the last few years has been much improved. See discussion boards. Optics Planet and many other vendors sell them.
http://www.leapers.com/index.php
I have a 2-7X Nikon scope on my 300 Blackout.
Want to add a Nikon 4.5-18X scope for my AR in .308.
And would recommend the American Defense quick release attachment. You can easily remove and attach your scope similar to an EOTech and it will not lose zero.
http://www.midwayusa.com/s?dimensionids=4294845682&newcategorydimensionid=6795