magic penetration from boots and void's staff go well with fiddlesticks passive and abyssal scepter.
spell vamp synergizes well with drain and his ultimate.
all his spells benefit from the slow given by rylai's.
pretty offensive build, but who can handle a op fiddles?:P

soon i'll be adding more info.just try the build out and see how fun it is to be fiddles.
he´s my favourite champ and i don't see him much in games nowadays.