Building your own flamethrowing pistol is most assuredly in the "Don't try this at home" category of weekend projects. But that shouldn't stop you from watching this video of someone who thought it was a marvellous idea.
Its copper construction and compact design gives off solid steampunk vibes, if you can ignore those almost suffocating tempting-serious-injury vibes.
I can't imagine this being a very effective weapon, though it might act as a good deterrent. I guess you could cook with it, if you were patient and completely unaware of magical devices such as stoves and microwaves.
A guide on how to construct this thing is available on Instructables, though we can hardly give you our blessing if you decide to pursue its creation. Between the law and its natural affinity for explosions, you won't get far.