It took me forever to come up with this post's title. "Young Guns vs Old Ones" is a small webgame where you play a role of five hot "new media" agencies trying to get through the block and kill the old guard by throwing media at them. Bizarre, I know. The coolest thing is that you can put your own ad on that poster you see on the screengrab.
If you liked it, check out Creative Bushido, an advertising strategy game by Yomiko Advertising.