Not really sure if this idea has been already posted, sorry if it already has.
Anyway, it's a combination of a simple Get to Objective and then Defend Objective type game, then Escape. This sort of scenario is often found in RTS games.
I've tried it in a 2v1 situation (2 ppl stopping the other guy from completing objective) and it works ok; would probably work better with more ppl and a larger playing field - I play inside my house.
To make explanations easier, Team 1 is the team trying to get to and then defend the objective, Team 2 is the annoying team.
Team 1 has less players than Team 2, but better equipment. When I get my friends over, the person in Team 1 gets to pick his/her weapons first (at least 2 per person if possible). Team 1 starts with only 1 weapon per person, the rest is next to the objective. Team 2 get the remainder of the weapons.
You can use whatever method of 'killing' someone (I use 2 shots to body or headshot) you want in this game - it should work fine.
Part 1: Getting to Objective
Time Limit: Depending on size of playing area, my indoors one is 2 min
Team 1 Respawn: Return to Spawn point, count to 4, re-enter play
Team 2 Respawn: Return to spawn point(s), count to 8, re-enter play
Size of playing area: Whatever, but musn't be too large - if Team 1 ppl get hit just before the objective, you shouldn't make them run like 2km to respawn.
Team 1 Spawn point: As far away from the Objective as possible; shouldn't be more than 300m at very maximum (unless everyone's an Olympic long distance, high speed runner)
Team 2 Spawn point: Away from the Objective, but not too far. They are defending it, after all. Musn't be too close to Team 1 Spawn.
Objective location: Away from the centre of the field, but far enough away from obstacles like trees that it has a large square area around it (for part 2).
How it ends: Member of Team 1 stopping timer (in obvious place in Objective) before timer ends, signals that Part 1 is over and begins stopwatch (see part 2).
Scoring: However much time left from the timer when Team 1 reaches Objective is added to their Part 2 time. e.g. if the timer is 3 minutes, and it's stopped at 1 minute remaining, Team 1 gets 60 points (60 seconds per minute).
How the rest of the stuff works: Team 1 spawns first and has a ten second head-start. Team 2 then spawns and tries to stop Team 1. Note that Team 1 should be able to get to their Objective within the time limit. If not, they lose immediately. Team 2 members are NOT allowed within a certain radius of Objective (depends on size of playing area)
Part 2: Defending Objective
Time Limit: A long time, but not TOO long
Team 1 Respawn: Return to Spawn point, count to (2-10, depending on no. of players), re-enter play
Team 2 Respawn: Return to Spawn point, count to (2-15, depending on no. of players), re-enter play
Size of playing area: Whatever you want, but Team 2's spawn point can't be too far from Objective.
Team 1 Spawn point: Away from the Objective, but not too far - they ARE now defending it, after all.
Team 2 Spawn point: Far away from Objective, but not too far - running long distances is a pain. MUST be further than Team 1's SP
How it begins: Team 1 member stops timer, records time remaining, signals Part 1 is ended (and therefore Part 2 has begun) and everyone knows that spawn points have now changed location. Everyone moves to their relevant new spawn point and match continues.
How it ends: Team 2 member enters Objective and stops stopwatch; timer goes off, in which case play moves on to Part 3
Scoring: Time on stopwatch is added to Part 1 score to make a subtotal score. If timer goes off, the time set on the timer is added to Part 1 score for a subtotal score
Part 3: Evacuation
Time Limit: NA
Team 1 Respawn: NA
Team 2 Respawn: Return to Spawn point, count to (5-20 depending on no. of players)
Size of playing area: Whatever you want
Team 1 Spawn point: NA
Team 2 Spawn point: Away from Objective AND Escape Point
Escape Point location: Either at or past Team 1's original Spawn point
How it begins: Team 2 member reaches Objective or timer goes off
How it ends: All surviving Team 1 members reach Escape point or all Team 1 members are 'killed'
Scoring: The no. of escaping team 1 members is multiplied by 10 and added to the subtotal score to give a total score.
How everything else works: All players MUST know that Part 2 is over, and Part 3 has begun. When Team 1 players are 'killed', they are removed from play. They must exit the playing area and watch without interfering. If ALL team 1 members are eliminated, they automaticaly lose and their score becomes irrelevant.
Part 1 simulates reinforcements coming to save a location from being overrun by enemies, Part 2 simulates defending the location until everything is prepared, Part 3 simulates the evacuation of the location. If the timer goes off in Part 1, the Objective is overrun by enemies. If an enemy reaches Objective in Part 2, it simulates a breach in defences and that evacuation must immediately begin. If the timer goes off in Part 2, it simulates that all evacuation processes are prepared. If a team 1 member escapes, it simulates an escaping evacuee(s). If all team 1 members are 'killed' in Part 3, it simulates the enemy killing all evacuees.
This generally only works if Team 1 is a smaller team, but may work with equal teams (I don't know).
I will update this post when I try a 2v3 situation.