Great topic SharkyMcShark

I really loved micromaster combiners as a kid, sheer giddy joy in creating a space shuttle tow truck

I also really liked the turbomaster/predator missle launchers. They really packed a punch and I used them to shoot down all sorts of things.

I never owned one but the G2 Aquaspeeders water pistols looked like fun

Finally just combiners in general were probably the most iconic and mindblowing of all transformers gimmickry.