I think it might be useful to have such a list.
Here are a few to start with,

Dead Weight, I had watched this on tv for years but it wasn't until I saw it online recently that I found out the victim had been wrapped in clear plastic and fixed to the back of a secret revolving door, only seen very briefly, which is a strange thing to edit out when the same thing is done with the victim on Cries Wolf but is not edited out.

Double Shock, the terrified reaction when the victim is being electricuted, same thing, I discovered this by chance online.

A Trace of Murder, when Clifford talks about bullshtting around, never seen it without the sound distorted.