Well this all depends on what you and your friends like to play, everyone likes a game of zombie so [erhaps you could recreate a game variant as I know of called Doors 1.34.16 (and loads of other random numbers), for this you use High Ground. Basically you barricase up the hole in the bunker (the giant hole that looks as if a bomb has hit it) so that it is nearly impossible to break it down, even with the use of a grav. hammer. You also need to place one of them large crates (the green ones) underneath the hatch and place a few palettes on top of then so that when the zombies attempt to break it via the hatch, their attempt is thwarted by your forging skillz =]. Now you move on throught the main gate and place 2 or 3 barricades in front of the door on your left, so the zombies can still break in but they will find it difficult. As you move further up he map (towards the inactive missile launcher thing) there is another door on you left, you need to place something on the inside of the door, that when everyone is inside (which needs to happen fast!) you can close it by pushing/meleeing something in front of the door CAREFUL the zombies will easily be able to break through this (but thats the point, you need to give the zombies a chance =]), do this for the next door as well. now you are inside the main base. Go up the stairs on your left you need to place a green large crate on the outside of the door that is straight in fornt of you, there shold be a balcony type thing when it will sit. Now if you take the door on your left, once you got through that door, there is another door on the left through that one you need to make a tunnel between both of these, again fairly indestructable, also for fun you could add some propane tanks so if the zombies break in and get that far you can blow them up for kicks. Then as you did for the the 1st two doors make something that canbe pushed/meleed to block up these doors. There is another door on your right as you enter the final room, place a large green crate outside of this one (as you diid for a previous door) then go down the stairs ad you will see a large gaping hole... this needs to be sorted or the death is inevitable, block this up however you can and with what ever you can, use trucks, weapon case, hey even use some fusion coils so one wrong swing of that energy sword and zombie is sky high =]. Now go back and fortify everything, add some scenery (barrels, pallets, boxes etc) and add some weapons, now be careful with the weapons you select, if you pick loads of heavy weapons it may lead to and early zombie breach as some noob has fire a rocket at YOUR barricade but at the same time, dont leave the survivors with pistols, thats just harsh. Now for the rules, you need the alpha zombie to be a fat kid (high gravity, low speed, loadsa shields so he liek invincible exept from assasination and he needs a grav. hammer and a sword), all the other zombies are exact opposite (low gravity, high speed, now shields so they are one shot kill but they only need an energy sword). The base player traits are normal, normal shields, normal colours etc but you can choose their weapons. Sometimes taking the base player radar off add a little of excitement to the game =] Now you should have yourself a kick ass game and game varient!
If you need any help or didnt understand what i meant in any of this but you still like the idea add me my gamertag is II KuRoSaKi II -- the lines are capital i's, just add some text when you add me saying something like, yahoo answers, or forge.
