Picture:

Gameplay Video:
http://www.youtube.com/watch?v=ynrF2es08ds
I think by now, most people have, if not played, at least heard about Team Fortress 2. The long awaited sequel to the original, the game was released by Valve along with Portal and Half Life 2 (and expansions) in the Orange Box. Team Fortress 2 was the multiplayer component of the Orange Box, and featured a combination of arena style first person shooting with humor and near flawless game design. I have yet to meet someone who said they did not like playing Team Fortress 2, and this really speaks to how good of a game it is. With its extremely well designed (albeit few) maps, hilarious characters, well balanced classes, and team based goal oriented gameplay, Team Fortress 2 has consumed many hours of my time and is certainly one of my favorite, if not my all time favorite, first person shooters.
Wireframe of GUI:
Larger Version:
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1: This GUI element is only shown when the player is playing as the Engineer class, and details all of the available deployables to the engineer, their health bars, ammo, and other relevant information.
2: This is a series of fading boxes that show when a player has killed a player of the opposing team, and with what weapon that player was killed.
3: This is the chat area, and is where players can communicate with each other, with the two options being team chat or general chat.
4: This GUI element indicates what class the player is currently playing as, and how much remaining health the player has.
5: This GUI element indicates the teams' scores, and the indicated the points of interests on the map with arrows that swing around in a circle depending on the players location to the POI
6: This GUI element shows the ammo count and metal count (the metal count is shown only if the player is playing as an engineer). The two numbers in the ammo count box are the current ammo in the clip/the total ammo the player is carrying
7: This GUI element is the timer. Not shown in the gameplay video, if there is a time limit placed on the map, it shows up here.