HmC's gm_flatgrass is a sandbox map which features a pause menu to allow you to spawn objects.

This map may seem boring and bland, but you are able to spawn sctructures, weapons, missions, vehicles, bipeds, ect. 

the Rcon password is pre set to password.

Additional spawn items to use object_create_anew with in devmode:
d1
d2
d3 - spawn dracos

w1
w2
w3 - spawn warthogs

sky - spawns a turret in the sky

arwing1
arwing2 
arwing3 - spawns arwings

scarab - spawns a scarab

Credits:

ILLEGALLcheatsMAN for level design, scripting, and magic afro tags
Hayabusa for halo 3 assault rifle and sniper rifle hidden in the map, also for encouragement
Jayden for scarab tags
fleetadmiral bacon for draco tags
Tiamat for pelican tags
Cmt for their numbers bitmaps
Halohogger for assorted area series bipeds
STW for multicolored ghost tags
l283023 for rigging ILLEGALLcheatsMAN's Voidberg biped model(spawned with the "spawn an emo" button)
Hazard for encouragement
HaloDoan and valve for the awesome combine biped :D
all of HmC for beta testing and spotting out errors
and to whoever I have forgotten to give credit

This map is made by the Halo map Customizers
