Since the release of the full Source SDK from VALVE (developers of Half Life 2 and Counter Strike Source), programmers and modders have been experimenting with the source code lately. I myself with trying to make my own modification for Half Life 2. While viewing the source code, I noticed several comments and code related to Team Fortress 2, a game which was supposed to be released years ago. One of the first interesting code I spotted about Team Fortress 2 was about a new weapon or utility which probably will be included in TF2. This is the shield. According to the source code, you can carry a shield around and also attack with the shield whilst on. According to this code "Shield_Knockback" (Image) you can probably use the shield, itself, to attack enemies with it.

Team Fortress 2 Revealed