Sam's Knife
From Super-wiki
The curved blade seen held by Sam in one of the main Supernatural promo images, and packed in his bag in the Pilot when he's leaving the apartment in Palo Alto to go with Dean appears to have no significance beyond looking cool. It is seen only in 1.01 Pilot.
You can buy one from Spytech-UK.com, where it's been labelled 'Alien Claw' under the category 'Fantasy Knives'. It also seems to be known as "Klaww of Death" by some online retailers!
The knife may actually be a suan ywe gou, described in weapons control regulations as "an article consisting of a curved blade pointed at both ends with a handle attached to the middle".
