Why the Batman can't kill the Joker and vice versa

Apparently This Fan Theory (nicely explained by igormorais) is now official cannon and has been explored in Arkham City, but I still think it is a really cool idea.

Valve Just Did Something Cool

They did a comic about Team Fortress 2, lets call it The War Administrator.

40 Years of X-Men In PDF

Yep Amazon.Com is selling a 40 Years of the X-Men DVD. That's:

• Over 485 complete printable comics, cover to cover, that’s over 17,500 pages.
  
  
• All X-MEN comic books from September 1963 through August 2005, including debut issue.

So certainly one to keep an eye out for. And if you read one comic a day in sixteen months your knowledge of X-Men would be almost completely unravelled.