G1 Megatron. I wanted Optimus so bad, and he was so impossible to find at stores. My aunt told me she bought me "that Transformer I wanted" for my birthday, so I spent a week anticipating finally getting Optimus. I tore open my present on my birthday and to my horror, it was Megatron. I completely overlooked the coolness of Megatron due to wanting (and thinking I was getting) Optimus so bad.
G1 Optimus Prime. Still have the original box, the Prime has been replaced over the years as he got a lot of play. Then Snarl. Then Runabout.
G2 Brawl. Or Dreadwing. Can't remember which one I got first, but I know I kept Dreadwing a while longer 'cause I used him in a stop motion flick I made in 5th grade. When I got back into collecting 1 year and a half ago, I started with Movie Incinerator
Armada Supercon Optimus Prime. Then I stopped after Energon Hot Shot. Then I got back into TF with the Movie. The first was Barricade and '77 Camaro Bee. Bee came with broken Automorph.
g1 prowl, first restart toy (new) was dvd mp optimus, but g1 trailbreaker was the first one in my collection now
Armada Hot Shot. All bad-articulation goodness that I still love even when most of my TF's are significantly better than him (exceptions being the G1 Duocons, who I got because they suck so bad. Hey, I needed a minimum standard to show where I draw the line!)