it is possible to create a piston that constantly extends and retrakts.

To construct it you need a Stiky piston a slime block and a redstone block.

Place the slime block infront of it and the redstone block diagonaly above the piton atached to the slime block. than update the piston tith a Block update.

it is possible to togellsuch behavior with a redstone signal.

it is not therystable because a new block update will destroy it.

the redstoneblock also creates a 0-tick pulse every time it is pushed.

it works in all directions eceptdownwards.

this behavior can also sustain itself after reopening the world.