Battery gimmicks are certainly up there but for me it’s clip on armour.
It’s either wasteful and unnecessary for the figures as it takes away from the budget and size of the toy or adds unwanted costs or it’s a silly gimmick that will end up with bits and pieces of smal plastic pieces falling off, breaking or getting lost by either adult or child fans.
I’m talking more about the RiD style minicon armour sets or even the power of the primes junk more than something more like a shell of armour like ultra Magnus.
I also hate enormous, stupidly absurd weapons such as what we got in the third transformers live action movie or even the combined wars/prime trilogy weapon/armour add ons.
Looking For: Wreckers Saga TPB Collection (with Requiem)