This is Mafia. I created this game to match what I used to play on Coagulation in Halo 2, and the first Mafia map on Standoff in Halo 3.
It is similar to Cops and Robbers, but the cop arrests the Mafia members for doing something wrong. Official Rules are below.
The gametype allows for the Mafia Member to be killed and that member turns into a cop, which makes teaming up on the last man standing fun and challenging, as the last man standing also runs at 300%. The custom powerup gives anyone a max of 150%, and any armor color turns to red, the mafia member color of armor.
The first Mafia map is available here

One rule that is helpful: NO GUESTS ALLOWED, except if the party leader has a guest. You must have a microphone, so that you can give orders if you're a cop, or tell a cop that you are going to jail. If you don't have a microphone when you play this game, it does not play correctly, and chaos erupts.

"Mafia 2" Map Variant
"Mafia" Gametype
This is best played with 4-6 players.

How the game works
Mafia spawn up in their sky base, either in the middle of it, or near the vehicles. Cop spawns in or outside the Police Station (The Blue Base). The Cop must watch for them to do something wrong, and go arrest them. He can use force if necessary.

Locations:
1) The Jail is located in the Red base, and the teleporter to the jail is located in the Police Station, the first one you see when you walk in. To be released from jail, the cop can remove the crate from the teleporter in the middle of the Police Station, above the normal walkway with a gravity Hammer, or it is possible to have another Mafia member bail you out...
2) Extra weapons are located through the teleporter on the left when you walk into the Police Station.
3) The Mafia Base is floating in the sky, and can be flown up to with either the mancannons set up, or the mancannon closest to it on the canyon wall of the actual map.
4) Vehicles for the Mafia members are located through the boxes in their sky base, either down or across. Across leads to a banshee pad, down leads to land vehicles.
5) Drugs are located inside the cave in the middle of the map, inside of 2 boxes. There is a new type of drug for this map, the spiker is acid.

Basic Rules:
1) No Driving off the roads (Roads are now marked by explosives on the side, creating a large area for everyone to drive in.)
2) No carrying "drugs," excluding cops (See below for list of drugs)
3) No attacking cops or killing other Mafia Members.
4) Mafia members may not use Hornets, but are allowed to use Banshees.
Drugs are:
1) Plasma pistol-Marijuana
2) Magnum-Cocaine
3) Needler-Crystal Meth.
4) Spiker-Acid
More rules:
1) Cops may never attack a Mafia Member unless that person is trying to assassinate them, or are being defiant.
2) Cops may ask for people to stop at any time, but only if the person may be not following the rules.
It IS possible to break out of jail, and it can include the death penalty if the escapee is found by the cop.
3) The last man standing can be killed for no good reason, because the last man "injects" himself with steroids to run at the increased speed of 300%
4) All players cannot see the names of their teammates until they are close, so from a distance, a cop using a custom powerup will show up in red armor instead of blue. Creates a sort of undercover idea, and allowing anyone to run faster with 150% running speed.

Pictures:

Mafia Base overview - This is the top part.

Mancannons and the hole in the middle of the base - jump up through this to go to the Mafia base.

Mafia banshee pad

Mafia vehicle pad

Vehicles are launched out of the boxes, creating a quick escape. NOTE: Choppers are supposed to hit the energy blockers, otherwise they fly off the edge!

Outside of the Jail - Mafia members can visit prisoners with the "window" in the energy blockers.

Drug cave - get drugs in the boxes

Cop vehicles

Teleporter exit out of jail - use the gravity hammers to hit the box off of the teleporter. Teleporter has fusion coils behind it to assist in removing of the crate.

Jail teleporter - This teleporter leads to jail

Weapon room teleporter - leads to the weapons room

Weapons room

Weapons room again

Mafia 3 is on my file share for anyone wanting to download, but I don't like it as much so I'm not even going to post it.