I was thinking of Hikari Touno, from Super Mobile Legend Dinagiga. He didn't even know who she was.

...Then again, Dinagiga is a /super/ obscure show that was canned after two episodes. Would that be considered cheating?

I tried various characters ranging from the obvious (while experimenting) to the relatively obscure, and it got them all.

+ Amy Pond (Doctor Who - knew it'd get this, just playing)
+ Haruhi Suzumiya (TMoHS - similar to the above)
+ Asuka Langley Soryu (Evangelion - a little more obscure)
+ Professor Nick Cutter (Primeval - okay, this one got to me, the questions it used to guess him seemed almost irrelevant. I guess that's the wonder of iterative refinement...)
+ Abby Sciuto (NCIS)
+ GLaDOS (Portal)
+ Admiral Parangosky (Halo novels)
+ Ezri Dax (ST: DS9 - to see if it'd distinguish between Jadzia and Ezri. Once it asked 'was your character murdered?', I knew it was on to me!)
+ Ilsa Pucci (Human Target - it went around in circles for ages, and I thought it wasn't going to guess right, but it did in the end.)

So far, the game has got:

*Navigator Presley (Mass Effect)
*James Raynor (StarCraft)
*Admiral Gerard DuGalle (StarCraft)
*Fleet Admiral Castor Dane (Metroid Prime)
*Metroid Prime (the eponymous villan of the trilogy)
*Samuel Vimes (Discworld)
*The Luggage (Discworld)

...right on the first try. I've managed to stump it once with Captain Kirrahe (Mass Effect) and Zeratul (StarCraft) but it got them right after asking a few more questions.

The best I did was with Alexei Stukov of StarCraft: the game needed three tries to get him right.

How is Scooby Doo inappropriate?

Which is sad, because it's a really cool concept.

It guessed Son Goku, Uchiha Sasuke, Varian Wrynn, Beka Cooper, Sweeney Todd (although that may have been a gimme), Lúthien Tinúviel, Jeanne d'Arc (probably another giveaway), Glorfindel (I need to stop using elves), Prophet Velen, Molly Weasley, and even my grandmother.

He didn't guess Chief Investigator Chris Jansen, although he came close a few times. He also couldn't guess Saraiyu or Dovasary Balitang from the Trickster duet, despite knowing both characters.

I... I love this game...

I spent a good hour on this, trying to figure out the most obscure characters to test this thing with. These were the results:
Harry Kim (Star Trek: Voyager)-Yep, they guessed it.
Legolas (Lord of the Rings)-I didn't expect to fool them on this one.
Kili (The Hobbit)-Darn, they guessed him right.
Mary Sue-They didn't guess Mary Sue! Someone should add it to the database.
Lindir (The Hobbit)-Lindir was a random hot elf in The Hobbit. It either guessed Legolas or Glorfindel.
Benedict Cumberbatch-Darn. I guess he's too famous.

It guessed Allen Walker from D.Gray-Man in two rounds and Mrs. Hudson from Sherlock in one. It couldn't guess Stephen Moffat though.

I stumped it with Naal'suul Val'Beldrobbaen from Drowtales, Ixpellia from Nanoha, and Carim Gracia (also Nanoha.)

Though, it's weird. It asked me if Ixpellia from Nanoha had red hair (yes) then asked if she had black hair. THen, it asked if she's a female (yes) then if she's a male!

I keep getting "I know who you are thinking of, but I believe this is not for children" on completely safe for work things, like Adam Savage and the main character of this really unknown duo of books, Green Angel and Green Witch. It also guessed Cut-Me-Own-Throat Dibbler when I was thinking of Twoflower, so it was in the general vicinity (Same book series, but I'm not sure if the two have ever met), but not what I consider close.

Also, someone I know used to be on it, but I think they removed him again.

It guessed Captain Jack Harkness, Alice in Wonderland and Amaterasu from Okami. Guessed wrong on Wolf from 10th Kingdom and Bernard from Black Books. It didn't know Umrao Jaan.

It guessed Radagast the Brown (from LotR) and Naoe Kanetsugu correctly, but failed to find Jernau Morat Gurgeh (from The Player of Games), Kai Wren (from Lord Demon) and Sam from Lord of Light.

I was thinking of the Sunflower Official. Do I get a prize?

But dang, he's good. He guessed Sora, Arcade Gannon, Bloodwing, and Sorin Markov before I picked the SO. =

It even guessed background charicters right! So, in order as I did them:
The Doctor (I knew he would get it, I just wanted to see how he worked)
Twilight Sparkle (same as The Doctor)
Derpy (to see if he knew background charicters that were popular. He did.)
Octavia (my first true attempt to get him. It did not work.)

Try your luck if you want, he is realy, realy good. I knew quickly when he got me: there will be one question that completely reveils who he thinks it is, and you know he's got you beat. Fun to play though.

...Hey, you think Jay or Accadia would be in his databanks? I'm not sure if I know them well enough to try, but if someone else thinks they can try, why not throw it his way? If he does not, you can add questions to lead to your answer, so the PPC can invade the genie's lamp. So to speak.