While use of the gibbet for humans is long gone in the UK, its use for animals was common in the East Riding (Yorkshire) into the 70s, and may still be for all I know. A local giving directions would routinely say to turn (or to keep on) at the gibbet.

Beside many a keeper's or gatekeeper's cottage and the ways into woodlands, would be nailed up battens of bird and small mammal corpses. They stank in warm weather, and I doubt that they had much of a deterrent effect on the wildlife (as some said they were supposed to) though they were often a useful waymark, and doubtless gave pause to the more casual trespasser.

I suspect that their real purpose was that the number of recent corpses should demonstrate to a passing owner or bailiff that a given keeper was doing his job.

The instantaneousness of execution by guillotine has been subject to debate. Tales are told which suggest that the head might retain some brief conciousness (such as that of two aristos who being beheaded in rapid succession, their heads were supposed to have been found to have bitten each other in the basket below the machine, having continued their mutual hatred even into death) but it would be hard to conduct any valid research on humans. Places where beheading is going on are not ideal for scientific observation. It is only fair to observe that the intention of the inventor seems to have been that execution should be quick and merciful by then-current standards.