voice actors J-K
Jackson, Samuel L. See favorites
The title character and Ninja Ninja on Afro Samurai; Zog in Astroboy; Gin Rummy on The Boondocks; Frozone in The Incredibles; Mace Windu in Star Wars: The Clone Wars (just the movie, not the series).
Johnson, Ashley See actresses I-K
Juliani, Alessandro See actors H-K
Gwen on Ben 10: Alien Force (and Ultimate Alien), Gretchen on Recess, Jinmay on Super Robot Monkey Team Hyperforce Go!, Terra on Teen Titans.
L on Death Note, Koji on Oban Star-Racers, Gambit on X-Men: Evolution.
Katz, Jonathan See comedians
Ultron on The Avengers: Earth's Mightiest Heroes, Mr. Herriman on Foster's Home For Imaginary Friends, Tony Stark and Ultron in Next Avengers, Monkey Fist on Kim Possible, Professor Utonium, Him, and Talking Dog on The Powerpuff Girls, Yoda, Admiral Yularen, and Narrator on Star Wars: The Clone Wars, Magneto on Wolverine and the X-Men, and no doubt other stuff...
Dean Dixon in an episode of Bob's Burgers, the title character on Dr. Katz, Professional Therapist, Erik on Home Movies.
Marty McFly on the Back to the Future TV series, title character on Danny Phantom, Dexter Douglas on Freakazoid!, Jimmy Olsen on Superman.
Yuzu on Bleach, Mui on Blood+, Mimi on Duel Masters (season 1), Ami on Hi Hi Puffy AmiYumi Show, Jenny on My Life as a Teenage Robot.
The first thing I remember her from is Viva Variety, which wasn't animated, but since then I've come to think of her pretty much as a voice actress. Gravitina on Buzz Lightyear of Star Command; the Bebes in an episode of Kim Possible; Tish's mom on The Weekenders; maybe some other stuff...
Ice King on Adventure Time; The Penguin on The Batman; Plastic Man on Batman: The Brave and the Bold; Crazy Quilt, Commissioner Gordon, et al. on DC Super Hero Girls (Sinestro in Intergalactic Games); Val Hallan on Dexter's Lab; Eduardo on Foster's Home For Imaginary Friends; Benjamin Bright on IGPX; Carl on Johnny Bravo; Zehos in Kaena: The Prophecy; Wally et al. on Mission Hill; Mandok and Sargous in Niko and the Sword of Light; Narrator, Mayor, and Mitch on The Powerpuff Girls; Griff on Rave Master; Heffer on Rocko's Modern Life; title character on SponegeBob SquarePants; Nute Gunray on Star Wars: The Clone Wars; Iron Man, Captain America, MODOK, et al. on Super Hero Squad Show; Gibson on Super Robot Monkey Team Hyper Force Go!; Mumbo et al. on Teen Titans; Starscream, Scrapper, Isaac Sumdak, et al. on Transformers Animated; Raimundo, Dashi, Hannibal Roy Bean on Xiaolin Showdown; and tons and tons of other stuff.
King, Regina See actresses I-K
Kreela in The Ant Bully; Huey and Riley on The Boondocks.
Kitt, Eartha See actresses I-K
Yzma in The Emperor's New Groove (and its spin-offs).
Kittie, Miss (aka Kali Bianca Troy)
Kline, Kevin See actors H-K
Trixie on American Dragon: Jake Long, Taranee on W.I.T.C.H..
Mr. Fischoeder on Bob's Burgers, Phoebus in The Hunchback of Notre Dame, Tulio in The Road to El Dorado.
Knight, Wayne See actors H-K
Zurg on Buzz Lightyear; Egghead on Super Hero Squad Show; Tantor in Tarzan; Al the Toy Collector in Toy Story 2; Dojo on Xiaolin Showdown; etc.
Kunis, Mila See actresses I-K
Meg Griffin on Family Guy (starting in season 2).