Window, dumb, stupid, key/map, or something else? I love the dumb tech with lithe or smash hit, because half the killers at red rank still swing at it, for whatever reason.
Corner tech and its variations is the only major tech frequently used when top players go against each other.
CJ and dumb techs are ridiculously useless against experienced killers. Window tech is slightly better, but majority of good killers play around it. Locker tech is extremely annoying, but very map-dependant and not quite productive for the purpose of winning the game. Minor techs were either removed from the game (nurse tech, old tractor tech) or are not relevant overall (spirit tech).
I have no idea what "stupid" and "key/map" techs are.
Edit: if you consider J-flick a tech, it's another relevant one.
Stupid tech is when a killer breaks a pallet, you run into it, crouch and run back, causing them to look behind them and swing when it works.
Key/map tech is when you use them to lose collision, and you can essentially go through killers when they break a wall. Also helps for easier window techs.
Key/map tech sounds okayish, I haven't heard of it somehow. Probably should have used these items more than once per 1-2k trials, huh.
I haven't considered stupid tech an actual tech, but it's somewhere around dumb tech level of usefulness imo.