These are mostly 1 vs. all, thats how I like to play.
One man versus 5+ other players. Other players guard a base (could be a flag, a hostage, anything) and Rambo uses a full auto marker (or ramping). (Optional) Rambo has to wear nothing but a tank-top.
Take parts of gun (barrel, reciever, hopper, tank, paint) and hide them in different places, using someone who isn't playing that round. Macgyver has to find the pieces and assemble them, while avoiding opposing team, then find the opposing team members and take them out.
One man has to carry at least 3 guns. Other team is in one base, Arnold has to take them all out using all 3+ guns.
One man has to be Chuck Norris, and roundhouse kick all other players. Chuck Norris cannot carry a marker, but others can.
One man is Homer Simpson, and others are guarding a can of Duff Beer (can be a can of Coca-Cola if under 21) and Homer has to eliminate others and get can of Coke and drink it.
Yes, I am running out of ideas.
One man dresses in purple and runs around singing, "I love you, you love me, we're a happy family..." while others shoot at him. Barney cannot carry a gun.
Hide a box of cookies, Cookie Monster has to find them. Cookie Monster can carry a marker, others also can carry. Other players have to shoot Cookie Monster, and eat the cookies in front of him when he has been taken out.
One man is George Lopez, and has to run around screaming stuff in Spanish. George Lopez can carry a gun. Other players take him out.
Tupac Shakur vs. Biggie Smalls:
Tupac runs around acting ghetto. The person who plays as Tupac has to sag his pants and wear a bandana over his mask, and shoot his gun sideways. A player on the other team has to be Biggie Smalls and kill Tupac. 1 on 1.
One man is Dick Cheney. Other people are turkeys. One man on other team has to be the old man. Cheney has to kill turkeys, but also shoot the old man.
Yes, I am almost out of ideas...
Okay one more.
North Hollywood Shootout:
2 men vs. 7+. the 2 men are bank robbers with full auto markers, 7+ others are cops. the 2 men have 20 lives each (can be hit 20 times and not go out), cops have 2 lives.