The chess game that is responding to builds

So back before the patches, people thought that reapers were overpowered because a reaper rush would 1. kill workers/work production and 2. force the opponent into getting roaches which are then hard countered by marauders which you make at the same building (tech lab rax).

I was curious about other similar strats where you do one thing early, forcing the opponent to do another thing, which you see coming and can hard counter easily. Something I've been doing recently against zerg is 3gate stargate then making one void to counter roaches, forcing them to muta or hyrda, phoenix if they muta, charge/storm if they hyrda. It's been working pretty well. I'd imagine there are others that involve things like FE or proxying which demand certain responses and knowing these responses are coming gives you an advantage.

Thoughts?