OMG Weapons! (and Monsters) is a small modification for Doom that adds extra weapons and enemies instead of replacing the standard things. Included are...
This modification is a tribute to the incredible Killer Quake Pack made way back in 1997. Although it contains 21 new weapons and 43 new monsters, it also features a unique random spawning system never before seen in Doom that does not require scripting, which works with the original and almost all user-made Doom and Doom II maps.
It is also dialup-friendly, with the downloading coming in at a mere 420kb. This was done by using ZDoom's editing features to recolour the monster sprites without needing extra frames.
OMG Weapons! (and Monsters) requires the latest unofficial ZDoom build, which is available at this location: Grubber.drdteam.org