What were those action figures called that were...?

Question

Those tiny robot dudes with the square patch on their stomach you held your thumb over to make the black patch turn into a symbol.

Answer 1

I remember transformers having those stickers

Answer 2

If the symbols you're remembeing were elemental symbols, then you are thinking of Battle Beasts. a bunch of animals in armor with weapons and sometimes what looked like cybernetic components to them. The figures were about an inch and a half to two inches tall and had the "heat sensitive" stickers to show you which element they belonged to. Also, the first answer was sort of correct in that the Battle Beasts were originally supposed to be part of the Transformers toy line back in the 80's.