TM M4A1 (New Type). It worked great right out of the box. Played a season and a half before my second fall on it broke the receiver. Then the madness of metal bodies and upgrading stuff started in earnest.
Knowing what I know now....I honestly wouldn't start with one now. I'd start with a Classic Army or G&P....run the stock mechbox until it dies (which might be very quick)...then just buy a drop in G&P or King Arms complete mechbox. I'd buy the drop in mechbox right away, with an extra grip and motor....then practice shimming and fiddling with the internals.
I have 3-5 favourites now...each with their own charms. Not in priority order, because I really do like each of them for their own things:
1. SystemA PTW M4A1...this thing is a beast, shoots incredibly far/accurate, it is now reliable and a solid go to gun.
2. King Arms Galil SAR (carbine length)...it's a great/gorgeous build right out of the box, the "blow back" system is solid and long lasting, it's handy/pointy and is different from a lot of the other guns out on the field. Just too much fun not to use.
3. WE M4A1 GBBR...gas blow back rifle. Tons of fun and great action. Solid weapons manipulation and "replication" of the real thing. Perhaps not the most accurate or long distance shooting of the bunch....but again, too much fun not to use.
4. WE KAC PDW, short barrel...gas blow back personal defense weapon. Much like a cross between and M4 with the compact bolt system of the SCAR...it's a pointy, compact weapon that shoots just as long and far as my WE M4 (sort of
). Folded stock...it's about as small as a MP5A3 (or any of the collapsible stock versions). As with the WE M4...it's just a fun, full of action platform to shoot.
5. Hurricane SHRIKE...basically a M4 AEG converted to a SAW/LMG. Honestly it's not much more than a regular M4 AEG...but heavier/bulkier. But you don't see many of them around...and it's not a common SAW like the 249 or Mk43 which everyone and their brother has. I've had a bitch of a time getting this to work decently...so it's more a labour of love than anything else at the moment. It's spitting plastic death as of last night....so all is right with the world once again.
Have fun.