Here's some I came up with off the top of my head, plus some examples:
Johnny Yong Bosch (Ichigo Kurosaki from Bleach)
Scott Menville (Robin from Teen Titans, Lloyd Irving from Tales of Symphonia)
Mark Hamill (The Skeleton King from Super Robot Monkey Team Hyper Force Go, the Joker from Batman: the Animated Series)
Steven Jay Blum (Spike Spiegel from Cowboy Bebop, Jamie from Megas XLR, TOM 2-4 from Toonami)
Tara Strong (Timmy Turner from Fairly Oddparents, Raven from Teen Titans, Sari from Transformers Animated)
Jennifer Hale (Sheena Fujibayashi from Tales of Symphonia, Sam from Totally Spies)
Dante Bosco (Prince Zuko from Avatar: The Last Airbender, Jake Long from American Dragon Jake Long)
Brad Swaile (Lan Hikari from Megaman: NT Warrior, Light Yagami from Death Note)
David Kaye (Megatron from Beast Wars, Optimus Prime from Transformers Animated)
Peter Cullen (Optimus Prime from Transformers)
Vic Mignoga (Edward Elric from Fullmetal Alchemist, Tamaki Suou from Ouran High School Host Club)
Crispin Freeman (Regal Bryant from Tales of Symphonia, Thomas Norstein from Digimon Data Squad)
Kyle Hebert (Kamina from Tenga Toppen Gurren Lagann)
Dan Green (Yugi Moto and Yami from Yu-Gi-Oh)
Tom Kenny (Spongebob from Spongebob Squarepants, Raimundo from Xaolin Showdown)
Phil LaMarr (Jack from Samurai Jack)
Keith David (Goliath from Gargoyles, Dr. Facilier from the Princess and the Frog)
...And yes, I am aware that it's a fairly long list..