Brilliant thread Skull! And of course you know who I'd have to go for =P
I'd be an Archer class servant. My Archer would be Anubis, the Egyptian Guardian of the dead. Anubis is of course of Egyptian descent fighting with a scimitar or bow. Legends say that Anubis was given Osiris' organs when the God of the Underworld.
Anubis wields a Golden Bow rumored to be given to him by Ra the sun God which is called the "Bow of Scorching." His scimitar has been infused with the organs of Osiris and can leech another Servant or Master's mana earning it the name "Sword of the Soul Eater."
Noble Phantasm->"Cursed Soul Shot" in which an arrow would be fired causing severe damage, cursing my enemy for eternity, and having them slowly bleed to death.
Noble Phantasm Variant-> "Eternal Shot" can only be used against airborne targets and is simply an extremely mana-depleting shot.
Noble Phantasm->"Judgment of Anubis" can only be used against a Master. It judges the Master's soul and forces them to either deal with their insecurities or perish with their sins.
Also I might point out that my servant is not a hero but more of a guardian spirit. Also instead of changing to spirit form and being invisible, Anubis simply changes into a big black wolf/dog.
Unlike most heroic souls that have been summoned before, Anubis is actually a rather friendly (and at times clumsy) Servant. Also he holds human like above all else and will not take the life of an innocent unless a command spell is used.
History speaks of the Servant Anubis/Archer having been summoned in one of the first Grail Wars and chose to kill his own master instead of letting the enemy kill her. Yes, Archer had fallen in love with his Master, but the corruption and destruction of the Grail War forced him to take her life instead of letting another unnamed Servant torture her. It's said that even as his Master laid dying in his arms, the Servant Archer (as he himself began to disappear) took down several opposing Servants and unleashed all his Noble Phantasms as vengeance.
A catalyst is required to summon me or you must summon me by traveling to the Egyptian ruins.