Background

I've recently found how to create a 1-time use trigger using a piston (must be pointing up) which pushes a redstone block:

The piston was too loud, so I'm currently using a hopper with 1 item that feeds into a chest:

Question

Are there any other "1-time systems", similar to the ones above, that are more compact than the hopper system I've shown?

Even if not more compact, I'm still curious as to other 1-time systems which can be used for builds.

They are way too easy - actually so easy they are an active problem when building. "Why does that not unpower?" is way too common a problem. It would be way too much work to list them all but I can post some silent ones.

Probably the simplest is repeater feeding itsef.

Every common RS latch will be this if you don't connect the R input to anything.

The classic repeater clocks become this if you trigger them with too long signal

If you want to use update instead of signal, a BUD'ed dropper with one item in it will react to a block update (and will be quiet when injecting that item into a container). After update it's powered and nothing can unpower it so it won't react to anything else, remaining silent.