Haha. I love this bug. It only seems to apply to corpses though but in HLDM it tends to happen if you get a kill with the crowbar. Blood goes everywhere!
My favourite glitch was one that happened years ago, towards the end of the game. An vort died near a rotating door and it jammed open. Then, whenever you stood over the vort's corpse your health would increase in single units (about 5 units per second)
My least favourite bug was with one of the early patches which made the game unplayable. This was around 1999 when I had no idea how to open the console (only my Dad's PC had internet access and it was a work computer)
You watched the intro sequence for 5 minutes and then at the end barney would walk to the tram and die on the spot. You couldn't get out of the fucking train! Me and my dad raged for weeks.
The best part of it was my Dad ended up setting up a LAN between his PC, mine and my sister's. My Bro-in-law, my Dad and myself spent 2 weeks playing Quake 1 from start to finish in co-op. It was good, there were many lulz. I know the game off by heart to this day.