One of my biggest problems with quake is how strong all of the enemies and the player are. Even the two basic enemies (the dogs and basic soldiers) require two shotgun blasts to get rid of. The player can wade through lava for a decent amount of time without dying. So, I made a mod (or am working on one, rather) which removes these issues. It is called FRAGILE QUAKE.
The very first release, version 0.01. This contains the mod, and two levels.
Here is the mod, with the first two levels. Just extract this into your quake folder, so you have Quake/FRAGILE/contents.