You can spawn stuff too...I'll post the NPC stuff for now, and I'll get the normal props up later.
NPC Spawns:
Hit tilde “~” and type "npc_create npc_ [name]” to spawn an NPC. Here is a list of the names you can enter for [name]
"alyx" (Alyx Vance) 
"barney" (Barney Calhoun) 
"dog" (Dog) 
"kleiner" (Dr. Kleiner) 
"eli" (Eli Vance) 
"mossman" (Judith Mossman) 
"monk" (Father Grigori) 
"citizen" (Citizen) 
"headcrab" (Regular Headcrab) 
"zombie" (Regular Zombie) 
"zombie_torso" (Regular Zombie Torso) 
"headcrab_fast" (Fast Headcrab) 
"headcrab_black" (Black Headcrab) 
"headcrab_poison" (Poison Headcrab) 
"fastzombie" (Fast Zombie) 
"poisonzombie" (Poison Zombie) 
"antlion" (Antlion) 
"antlionguard" (Antlion Guard) 
"combine_s" (Combine Soldier/Combine Elite/Prison Guard) 
"metropolice" (Metro Cop) 
"stalker" (Stalker) 
"cscanner" (City Scanner) 
"manhack" (Manhack) 
"rollermine" (Rollermine) 
"combine_mine" (Hopper Mine) 
"combine_camera" (Combine Camera) 
"turret_floor" (Combine Turret) 
"turret_ceiling" (Ceiling Turret) 
"turret_ground" (Ground Turret) 
"launcher" (?) 
"combinedropship" (Dropship) 
"combinegunship" (Gunship) 
"strider" (Strider) 
"pigeon" (Pigeon) 
"crow" (Crow) 
"seagull" (Seagull) 
"barnacle" (Barnacle) 
"ichthyosaur" (Ichthyosaur) 
"vortigaunt" (Vortigaunt)