Raptors replace the regular fiend/demons in the levels. Sound effects were taken right from the movie. This patch is really cool.
Drones are models that have to be put in a level to work. It comes with a sample level, so if you can't or don't feel like making a level, you can see it.
The Blarg has the best sound of any model I've heard. The look is so original.

Hear for yourself
The Blarg | A Blarg Level | Another Blarg Level
Mechwarrior 2 is a large file but is well worth it. You ride around in a huge Mech and use the original weapons accompanied by the sound that were in Mechwarrior 2. Get it.
Mechwarrior 2
The Dragon is a very well animated model that has to be put into a level to see it. Comes with a sample level.
The BoBomb is the walking bomb from one of those Mario Brothers games. It doesn't have the legs but is neat. You can either build a level for it or replace the grenades with this. That's what I do.
The Alien Fiend is a different skin for the fiend. It is a sample from the Alien Total Conversion. The only difference is that it has no horns. But this looks cooler anyway.
┐Remember the Cyber Demon from Doom II? Now it's here in Quake. Comes with a real level so you can view it.
Cyber Demon
Psionic Slug, who would have thought. It blasts you and others with a mental ring projection. The animation is very realistic and the colors are awesome. Doesn't need its own level. Replaces random characters in Quake Levels.
Psionic Slug
The Snake Man is a well done character that I believe has to have his own levels to work. A new skin was done that looked more like a snake. Both skins are great.
Snake Man | New Skin
Willy the Spider is a cool replacement for the Hell Knight. Uses the Vore/Shalrath sound which fit in perfectly.
Willy the Spider
The Anomaly replaces the demon with an free-floating spherical creature with cooing sounds. Really Original
Wildwing from the Mighty Ducks replaces the enforcer in the Quake levels. Excellent model.
Wild Wing
The wyvern rplaces 1/3 of the scraggs in each level. Cool fire breathing dragon.
Four New Fish Skins
Skin 1 Skin 2 Skin 3 Skin 4
A replacement model for the player which looks like Goliath from "Gargoyles".