Below is a list of pass parameters that I have experimented with. I'll put them in context later on. I just wanted to list them now so I may clean up my HD.
Pass Params Notes on :
undefined - crashes DO NOT USE!
sky - interesting, no texture, no reflextion
clearbuffer - no texture in reflection
rgb - no reflection
rgba - some reflection
rgb_texalpha - no reflection
rgba_texalpha - same as rgba
rgb_addvert - full white glow
fullmodulate - darkened reflection
fullbright - no reflection
rgb_add - brightened reflection
screenpoly - no texture, no reflection, but seen through walls.
rgb_decal - no texture, no reflection
glow - reflection, no texture, but seen through walls.
rgb_masked - texture, but no reflection
maskedwall - textured, no reflextion, but weird lightmap problems.
maskedlightmap - much like clearbuffer
addparticle - textured, bright reflection
subparticle - reflextion only, no texture
blendparticle - reflection, but no texture
addbeam - textured, bright reflection
lightmappedwall - light mapping works, but is buggy. No reflection
lightmap - loss of detail, no reflection, fullbright effect.
lightmapadd - same as above, but reflections work.
maskedwallrgb - no reflection.
rgb2sided - no reflection
full_texalpha - fullbright, no reflections
full_texalpha_add - fullbright, no texture
full_addconstant - blindingly bright, no texture or reflection, full light glow
lightblob - bright reflection, no texture.
shadow - dark reflection, no texture
zonly - full reflection, no texture
alphalightmapped - reflections and texture, but buggy lightmap.
addlightmapped - bright reflection, buggy lightmap.
detailmodulate - dark textured reflection.
solidglow - full bright reflection.
outline - completely white glow.
saturate_decal - dark reflection, no texture.
rgb_modplusdest - dark reflection, no texture on non-reflections.
full_modplusdest - bright reflection, no texture on non-reflections.
lightmap_mod - loss of texture detail, reflections are dark.
full_add - textured and fulbright with reflections.
lightvolume - same as above.
full_sub - realy dark reflection (darkest yet). no texture on non-reflections.