Naruto:
Naruto Uzumaki - ADHD (Attention Deficit Hyperactive Disorder)
Sasuke Uchiha - Mood Disorder
Death Note:
Light Yagami - NPD (Narcissistic Personality Disorder)
Light Yagami - Clinical psychopathy
L - Asperger's Syndrome
L - Marfan's Syndrome
Near - Albino
Soul Eater:
Blackstar - ADHD (Attention Deficit Hyperactive Disorder)
Full House:
Daniel 'Danny' Tanner - OCD (Obsessive Compulsive Disorder)
Teen Titans
Slade - Clinical psychopathy (yes, Robin called him a psychopath a bunch of times, but it was never technically confirmed.)
The Big Bang Theory
Sheldon Cooper - OCD (Obsessive Compulsive Disorder)

Hope you liked this! If you have any more ideas, tell me in the comments and I might add them.