[decepticon_mark]

I can't really say what my first was but I was thinking about it and I do remember the collections which made the most impact on my childhood days. They are in no particular order though.
Mego 8" Superhero dolls/figures
Star Wars, the original line from the 70's and 80's
GI JOE, again the original 80's versions
Transformers G1
Johnny West cowboys from the late 60's and early 70's

Had alot of other collections I dabbled in like Buck Rogers, Flash Gordon, TMNT, Inhumanoids, Thundercats, Silverhawks, and more but the above are the ones that really were my favs and made the most impact. Sadly a tornado at my mom's house robbed me of my Star Wars and Johnny West stuff and as a teenager I made the mistake of selling off my Transformers and GI JOE. That is a huge regret now.