There are quite a lot of maps that I looked at when I was working on my map, to see the way I wanted to design my map, and what sort of game type I wanted it to be based on.
2fort is a Capture the Flag map in Team Fortress 2, where one side is the same as the other, just flipped.
Quake 2 has what some cosider to be one of the best maps ever, called “Edge”. This was the first map I looked at once I had read the Brief.
Karkand is the most popular map in Battlefield 2, and Battlefield Play4Free, and was liked so much, that it was remade and added as DLC to Battlefield 3. This is the map I always look forward to when played Battlefield Play4Free.
Payload is my favourite gametype of any multiplayer game, so this isnt the only map that I like that suports this gametype in Team Fortress 2, but there are so many, that I just went for the one I have played the most to show what the gametype is like.
Some maps, like Crash from Call of Duty 4, are not ones that I would put up there in my favourites, but that I respect for how well they are designed to suport a few different gametypes, and pulls them all off farly well.