Here Is my Fiddle Build it is rare unique and always works...
As you will be able to see with my build it is quite weird more so the way I prioritise my items its pretty standard ruins splitting it with Magic Pene and Ability Power. I never take Flash and I always go Ignite and Clarity for my ability to uber stay in lanes and harras/farm.
I find this build gives fiddle more guts for late game.
I prefer to Lane with Fiddle but dont mind the occasional mid as well...
Start off with
Dorans Ring
Then I go back to shop and pick up a blasting wand and level 1 boots...
Then stay and farm or gank... return to pick up needlessly large rod and level 2 boots
Continue in lane until able to by hourglass... then the fun begins...
Fiddle is a awesome farmer and king of crowd control... this is where team fights should be commencing its time to suprise from the brushes and initiate over enemy towers or even your own defending them using your ulti. then spam your fear, followed by darkwin and finally drain...
If hitting there tower your team mates should be engaging them now its time to pop hourglass so the tower stops targetting you whilest your ulti still is going. this will deflect to another team mates then you can keep fighting this usually secures a tower for your team and ultimately at least 3-4 kills for your team or even acing them...
Defending Towers this is effective cause when you ulti and spam your abilities on them most people think its only fiddle and will try wipe you and the tower after i use all my abilites and they focus me I then crank hourglass so then the tower gets them by the time I come out of stasis there might be 1 left then they die (this does work I have pentakilled a full health team doing this whilst defending alone)
Then its time for Void Staff for Magic Pene
The next Items I go for depending on gold and game situation are either Rabadons Hat or Ryailis Crystal Septar - this gives you a slow on top of your fear silence and drain very nice...
Last Item is Haunting Guise for more magic Pene...

You should be dominating at this point usually the game is over before the 6 items if your team is half decent as you can see its a well rounded fiddle