Idea: Portal Multiplayer
if theres a team with a portal gun and one with a normal gun the map should be called.... CC_portal-vs-hl2.
(CC means capture cube)
but it would really require alot of thinking with portals to survive on the portal team...
he didn't mean a team with portal guns, and a team with weapons. he meant classes. like some people in your team could have portal guns, and some would have weapons but noone would have both
Is it going to be a :
-Random map appears.
-Choose map to play in.
-Limited Choice of maps, the more wins you have the more maps to choose from.
Which one?
Not in Wrath
The Reaper Came Today ;
An Angel visited
This gray path
An took the cube away''
- (Subject Name Here)
oh lol. then its fair enough 
-Random map appears.
-Choose map to play in.
-Limited Choice of maps, the more wins you have the more maps to choose from.
Which one?
-Random map appears. 
else every server a gonna play the same map because thats the "best" map...
yeah but its better to be allowed to ban custom maps or a few selected maps so they won't get randomized in.
Or else u can get the map you personally hate.
Map ban limit of 20% of your map folder? =D
Maybe different styles of gameplay? My favourite would be just run around, do whatever, like in Gmod.
Theres been alot of attempts at this.
Sandbox gametype would be cool yeah... With lots of cube, turret and ball droppers.
I can think of a multiplayer teamwork map...
Two players start at the elevator. After they walk through the door into a large room, GLaDOS comes onto the intercom and announces that the room is a broken test. After the comment is finished, a sewer pipe breaks, and the room begins to flood with goo. The two players have to cooperate to get to the top of the room and place two storage cubes on buttons to close the pipe. An example of the multiplayer element would be one player standing on a button, and another firing a portal through an open door so they can both escape. Once both cube buttons are activated and the sewer pipe vent is closed, GLaDOS congradulates the players for "staying positive in an atmosphere of extreme pessimism", 
. But then it starts raining Turrets, and the exit is blocked. One Turret accidentally breaks the hatch-closing buttons, and the room starts flooding again. The two players have to work together to get all the deactivated Turrets out of the way and escape into the elevator before the room is filled with goo. (There should be enough deactivated Turrets so that one player can't do it alone in time, and the floor and walls in the Hall of Turrets are portal-proof.)
*fifty cakes fall out*
Time out for a second. That wasn't supposed to happen.
There is a multiplayer tetris now.
Gametypes:
Cooperative
Sandbox
Incinerate The Cube
Hmm... how could a sort of deathmatch work out ok? I dont see any way for just deathmatch or team deathmatch. It works better with goals.
Domination from UTclassic like gametype. But instead of taking over the control points, its a regular portal button.
What about a map with only 1 Portal Gun? Everyone has a stunstick and when holding(not having in inventory) the Portal Gun you get points in time.