Butch's Toothpick is a unique variation of the Switchblade in Fallout 3. It's held by Butch DeLoria in Vault 101. It does twice the amount of damage a Switchblade does, however it's not very powerful for a melee weapon; there will be many better weapons for the Lone Wanderer to find when they leave the Vault for the Capital Wasteland.
It can be obtained by starting a fight with Butch and shooting the weapon out of his hand. It can also be obtained if you have Butch as a companion. All you have to do is trade equipment. If Butch is kept alive then the player can return to get the knife in the Trouble on the Homefront quest.