There are a few different types of servants I can summon depending on how I want to think about this:
Let's suppose we include all fictional character:
As some said, DBZ characters would be overkill but... seriously I don't like the concept at all... since they don't really fit the classes system. I mean there is no "martial artist" class (if we can still call that martial arts anymore...)
So let's suppose we can only include fictional characters that fit any of the classes:
Someone mentioned Link before... I have to agree at the awesomeness!
But I would mostly choose:
Class Berserker of course.
Strength: B+ ( A mad enhanced)
A (A+ mad enhanced)
Noble Phantasm: A
Mad enhancement: D (Raises strength and endurance by half a point but reduces thinking to a functional minimum)
Eternal rage rank B: This skill effectively nullifies any penalty from mad enhancement inferior to rank B. (Since he spent most of his lifetime in an enraged states, he gradually learned to live with it).
Instinct rank C: The instinct of a swordsman... can help him sense and avoid fatal blows.
Hidden hand Canon Rank A: A one use per fight skill enabling him to fire the hidden cannon in his hand. High damage output, cannot be reloaded in battle.
Tools of the mercenary: Rank E-D+, can use throwing knives(D), a repeating crossbow(E), miniature bombs(D+). These tools are mostly used as a diversion to allow to find an opening in his enemies than to actually damage them.
God Slayer: Rank C: His experience in fighting against divine creatures reduces the advantages of the divinity skill by one full Rank.
Dragon Slayer: Massive cursed blade forged to kill even dragons. Rank A / target (1-5 from sheer size).
Berserker armor: Rank B. target self. Raises the mad enhancement rank gradually until it reaches A. At this level the user can no longer distinguish between friend of foe. Once reason is lost (after reaching rank B mad enhancement) only the command spells can cause him to revert to his original state. While active magic resistance is raised to rank C and the user benefits from a short term regenerative ability with a damaging backlash after the effect is canceled.
I hope he isn't too imba lol...
On the other hand if only mythical/popular folklore fictional character (and characters from the nasuverse) are allowed:
I'd probably think Merlin would make a good caster.
But I'd totally go for Arcueid as a berserker... But since she is not human at all and never was... I don't think she can become a heroic spirit (and by extension a servant).
Or Nanaya Shiki as an assassin... He wouldn't have a noble phantasm but a skill that could be assimilated to one. Mystic eyes of death perception. It would probably allow him to kill even noble phantasms themselves. And he could use presence concealment by converting back to Tohno Shiki lol...
But then again... I think assassin can only be Hassan.
But if I need a catalyst or a have some form of relation to the servant... I guess the two most likely historical figures I could draw are Hannibal Barca since he's our national hero... And I guess if I'm lucky (and research enough) I might be able to get my hands on a relic related to him. Or Barbarossa since I was born on an island he made his base. (Wiki him as Barbarossa I since I can't link yet)
Hannibal would be a rider. And I think that most his skills and stats would be like those of Rider from Fate/Zero. He would call down a stampede of elephants! But well he wouldn't have any divinity... since he never was believed to have any... Actually I think the romans even considered him a demon for a long time.
For Barbarossa... I wouldn't know... I guess I'd need to summon him to see? lol
(Well with this... and some research... you guys can probably pinpoint my birth place)
Sorry guys for the long post... But getting back to uni is just depressing... So It's just helping me think about something else.