not a complete list, just some stuff that doesn't have it mentioned anywhere else, more complete version coming soon.

shotgun sounds are from half life 1 and hexen (denoted in sndinfo)

poison pellet sprites are edited sprites from jazz jackrabbit

poison gas, hellfire trail, hellfire shell shot (main missile, not starburst) are from hexen

elec.kvx from doom voxel project

ARWP.kvx, ARWQ.kvx, and ARWR.kvx by voxelbro from /vr/

//Sprites in "Sprite Fixing" folder in sprites are from the Doom 2 Minor Sprite Fixing Project - v1.4 by Revenant100 aka Marphy Black
SWBEEP.wav is from shadow warrior