1) When you die next to shadowfire and a zombie (possibly other monsters?) walks close to your dead body and through shadowfire then the monster takes elemental damage like players. I think that this bug may exist in other places with shadowfire as well.

How it looks like:
https://www.youtube.com/watch?v=sHDRnv46cG0

2) I think think this one is well-known already - the last room of 2nd depth in C42. Giant Toxoil behind gate on the top is too big and it's possible to damage it with Sentenza/AP for example (not sure about other weapons) and kill the Toxoil which results in openning gate that leads to elevator

How it looks like:
https://www.youtube.com/watch?v=eWuklIAjolA