CrazyEgg keeps it fun even in bad situations. Their "service down" page features a mini Flash game, to divert your attention and anger while you are waiting for the services to come back.
Spicing the mundane system error pages with jokes has become a good tradition for web-20. Here is a good blog about it.
What sets this example apart is that the game is custom-branded. And, since the chance of seeing it should be pretty low (ideally), the users may appreciate that extra time CrazyEgg puts in such things.
If you are interested in Flash games, or are looking for game engines to brand them for your site, visit www.theoworlds.com.