The oldest gimmick of all that still remains today: the 5mm post!

It is such a simple but awesome gimmick. A universal weapon post and fist hole size that allows Transformers to interchange and share weapons and accessories. The original G1 Optimus Prime and all of the first year Decepticons have 5mm post weapons, and thanks to Armada for standardising the 5mm post, now almost every Transformer uses 5mm post weapons. Just the other day I put my MP Grimlock's gun in my POTP Nemesis Prime's fist.