The Heckler & Koch G 36 rifle was developed as the standard issue for the German Army. It comes in several variations on the real-steel side, but that information is available elsewhere.
Here are some AEG's I have some first hand experience with.
JG G36C
I collected this one with the M-4 Magwell converter and crane stock pre-installed, in part because it was available and there seemed to be a growing shortage of AEG's and in part because I was frustrated by my M-4 conversion experiments with the SCR. As a short barrel model I thought it would be a nice fit for games like Plague, because it will use my stable of M-4 Mid-Caps. On an 11.1 li-poly it's got a great rate of fire. FPS is below 350, and I've enjoyed using it in CQB scenarios. While it's not a primary gun by any means it's held up to li-poly use so far.
It does not have the same level of fit-and-finish quality that the SRC model does, particularly in the stock...it's pretty wobbly. While I like the crane stock's looks, the fact that the M-4 converter kills your ability to fold the stock does limit its close quarter maneuverability.
Tokyo Marui G36C
Completely stock for the time being, this was a trade gun that's come to me thru two other owners and probably not more that three skirmishes. It's a perfect CQB set up, and only in the #3 roster spot for CQB missions because I like M4 mags better. The selector sometimes slips over into full-auto from time to time...something to look at fixing this winter.
JG G36K "Franken-Gun"
Frankie began her life as a CQB gun, but through a series of amputations, grafts, re-installations and modifications she's as good as new and better. Sporting an extended MadBull 6.03 Python Tightbore barrel extending out of the "C" variant front end, this beauty can reach out and touch someone. The Magpul AFG gives a consistent grip-point, and its light weight and stability makes it a joy to shoot.
This gun is my field-op back-up, ready to play in the event Maggie goes down with an injury.
SRC/TSD Tactical Gen 2 MK36 E2
Solid build, good fit and finish. Range and rate of fire is good. I replaced the gears (which were good and properly installed out of the box) with a Modify High-Speed set and upgraded the spring so it's shooting right about 400fps. The stock 9.6 battery couldn't handle that set-up, so I had to go to an 11.1 li-poly to get it skirmish-ready.
I wanted to put a M-4 Magwell converter on this gun, but I never could get it to work correctly. SRC has a special hop-up and you'd have to machine out part of the converter to make it fit. I didn't have the patience for it. I tried several hop-ups, bucking combinations and eventually decided that the standard G 36 mags would suit me just fine.
This gun has left my home for greener pastures.