I've made some research in leaked ep3 and hl3 related stuff, and here's the list.
###Weaponry###
weapon_proto1 "357.mdl" - A laser gun that could have had ability to see through walls and shoot trough them. Appeared in HL2 Aftermatch.
weapon_teleport "chargegun.mdl" - Return of Opposing Force's Displacer Cannon?
weapon_spygrenade - Unknown
weapon_pipebomblauncher - Almost nothing is known, probably was like tf2's launcher.
weapon_gauss "gauss.mdl" - Tau-cannon returns
weapon_flechettegun - A gun that had ability to shot hunter's flechette ammo?
weapon_egon "egon.mdl" - Gluon-gun returns too
weapon_flamethrower "flamethrower.mdl" - A flamethrower, nothing more.
weapon_icegun "icegun.mdl" - Not enough info.
NPC Weapons: dartgun, minigun, mortar, propeller, bomb, shield, RPG. - Npc weapons, almost nothing is known
item_ammo_uranium "item_ammo_uranium.mdl" - Tau-cannon and Gluon-gun ammo.
item_ammo_fuel - Maybe ammo for flamethrower?
weaponizer_concrete "weaponizer.mdl" - I still don't know what are these.
weaponizer_liquid "weaponizer.mdl"
weaponizer_metal "weaponizer.mdl"
###NPCs###
npc_combine_advisor_roaming "advisor.mdl" - Advisor with fully functioning AI.
npc_blob "blob.mdl" -Could have spawned tiny blobs, can merge with other blobs, can jump, had nests.(hives) Slimey creature that had brain and could spread?
npc_surface - Portal 2 gel physics test entity.
npc_blob_tiny "blob_tiny.mdl" - Tiny blob.
npc_blob_medium "blob_medium.mdl" - Medium blob.
npc_blob_small "blob_small.mdl" - Small blob.
npc_blob_large "blob_large.mdl" - Large blob.
npc_soldier_mid "soldier_mid.mdl" "margarita soldier?"
npc_soldier_large "soldier_large.mdl"
npc_soldier_fast "soldier_fast.mdl"
npc_composite_companion -almost nothing is known
npc_combine_armored "combine_soldier_armored.mdl" - Armored combine soldier, appears in half-life 2 aftermatch.
npc_wpnscanner - Weaponized city scanner, appeared in HL2 Aftermatch.
npc_quest_citizen - Citizen that could have given you quests?
npc_hunter_invincible - Combine hunter, but invincible?
npc_turret_celling_pulse - Probably an AR2 styled pulse celling turret.
###SFM REMNANTS###
hl3_movies - Is like tf2_movies foldier, probably for trailer and cinematics purpose?
dog_fight - I honestly don't know if it's ep2's dog vs strider remnants or completely new scene.
###Misc###
Zipline - It seems that you could have used a zipline in some places.
VR Mode - Maybe that's what hlvr will be?
Probably open world, i don't know for sure.