My first airsoft gun I ever bought was a TM Thompson M1A1. I still have it and I still love it. The first gun I ever gamed however, was a Classic Army M16a4 I bought from 007airsoft, when he use to carry them. I still use my M16, it has been upgraded and preforms well as my outdroor gun, its begining to show its age, but that only makes it look better(IMO), its been dropped a few times, but it still fires true!
I also like to use it as my yardstick to compare with new AEGs that get added to my collection.