I make my throwing knives from Mild Steel (low carbon) sheet. They are 35.5cm long, 6mm thick and around 255g heavy, the center of gravity is nearly in the center. The blanks are laser cut to size and then I do some work on the point end and generally clean off any burrs. When they are up to that stage, and I am certain that no more metal needs removing they then go for heat treatment whereby they are heated in a salts bath to cherry red, and the carbon soaks into the red hot steel. When a millimeter depth of carbon is introduced (this takes a set time), the blades are quenched in oil until completely cool. The blades are then glass-hard on the surface to a millimeter depth, with a soft core. This prevents burrs from kicking up on the blade. Finally they are sand papered clean, and I fit my stick-on handles (those are rubber-stickers I just have to peel off the paper, I have them made at a sticker company).
The throwing knives' sleek shape is the one that suits my throwing style best. That is No/-Quarter-/Half-spin throws! The shape allows easy sliding from the hand, both from the blade and the handle. The small hilt is cosmetic, and makes the throwing knife more "daggery".
A short note on Roy's special throwing style: He strives to reduce the rotation of his throwing knives nearly to zero. There is no arch in his throw, he pushes the knife to the target similarly to the movement you would use to throw a very heavy ball (shotput in sports). The index finger rests on the spine of the throwing knife, and it pushes down on it when the knife has halfway left the hand, to reduce the spin. With years of practice, Roy can throw no-spins from 5m and further.