An AR with a MagPul collasible stock is idea. Easy to shoot accurate,y, and the stock is much more adjustable than the standard M4 stock.
Also, if you are of short stature, consider an AK. They are simple, reliable and designed for shorter Russian soldiers. They lack the accuracy of the AR.
Another possibility is the Keltec SU-16. While not as accurate as the AR, they are very reliable and use easily obtained M16 magazines. They are very light - around 5 pounds, making them one of the lightest military style rifles made.
The Mini-14. like the AK, is not particularly accurate, but is fairly light and reasonably reliable. It lacks the after market parts the AR family has.
I've had a chance to evaluate a number of AR rifles made by the better known manufacturers. Believe it or not, one of the better ARs now made comes from Smith and Wesson. Armalight, Rock River Arms, DPMS all make good rifles. Colt is not at the top of my list.
What is your budget and intended use? My personal feeling is that a well maintained standard AR is just fine. The piston operated variants don't offer a significan advantage. If you want utter reliability above all else, get an AK.