I think it would have to be the Dreamwave comics that ignited my collecting habit as an adult. Had bought a few Beast Wars, Beast Machines, RID, etc over the years, but nothing much. DW's comics brought back the G1 characters, and in my opinion were the first step on the road to getting Hasbro all that sweet sweet Michael Bay movie money.
I dabbled with the AEC lines, mostly getting what I could at sales. Managed to get a couple of Classics, but wasn't lucky to have too much spare cash to go crazy on them. Once I started getting more money, I went back and looked at what I'd missed. I think Henkei Megatron was the first toy I bought off a web-store and things just started escalating from there.
assembling a Neo-G1/TF:TM cast. Please PM if you have (or know of) the following at a reasonable price: Classics or Henkei Prowl, Astrotrain, Ramjet, Skywarp, Sunstreaker, Sideswipe, Blurr, Perceptor, GDO Wheelie and Springer, or 3rd Party Motobot Arcee, FP Springer, iGear Ratchet and Ironhide, City Commander (and/or Ultra Magnus), Starscream (deluxe) Coronation add-on, or Spike and Daniel in their Exo-Suits.