Miniature Portal Gun.

They're actually not that miniature but they're much more inexpensive than the full size ones. You can pick one up at ThinkGeek.

Hobbit Slippers, $20!

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Portal Cookie Jar

ThinkGeek just rolled out a new Portal Cookie Jar, I think it's a must buy at $30.  For sale here.

Aperture Products.

The best merchandising a game or movie can do is something either straight out of it or something that would exist in that world.  I found these two gems:


Cave Johnson Portrait

Build your own GladOs Potato!

Both wonderful and both available at Think Geek, here and here.