Lastly, the movies... which being live-action and more expensive as guests, has the smallest proportion that have been at BotCon.
Already a couple deaths too.

Movies (2007-2011)

y Peter Cullen - Optimus Prime - 97, 04b, 06, 07, 09, 10, 11, 12
y Tyrese Gibson - Epps - 09, (11)
y Kevin Michael Richardson - Rampage, Prime #2 - 11
y Glenn Morshower - General Morshower - 13

(significant participation - more likely to be a good guest)
n Charles Adler - Starscream
n Patrick Dempsey - Dylan Gould
n Josh Duhamel - Lennox
n Kevin Dunn - Ron Witwicky
n Megan Fox - Mikaela
n Robert Foxworth - Ratchet
n Jess Harnell - Ironhide, Barricade (07)
n John Benjamin Hickey - Theodore Galloway
n Rosie Huntington-Whiteley - Carly
n Ken Jeong - Jerry Wang
n Tom Kenny - Wheelie, Skids
n Shia LaBeouf - Sam Witwicky
n Frances McDormand - Charlotte Mearing
n Leonard Nimoy - Sentinel Prime
n Ramon Rodriguez - Leo
n Mark Ryan - Bumblebee, Jetfire
n John Turturro - Seymour Simmons
n Jon Voight - John Keller
n Hugo Weaving - Megatron
n Frank Welker - Soundwave, Shockwave, Barricade (11), Ravage, Reedman, Grindor, Devastator
n Julie White - Judy Witwicky
n Reno Wilson - Frenzy, Mudflap, Brains

(minor participation - less likely to remember much as a guest)
n Anthony Anderson - Glen
n Greg Berg - Igor
n Ron Bottitta - Roadbuster
n George Coe - Que/Wheeljack
n Grey DeLisle - Arcee
n John Di Crosta - Scalpel
n John DiMaggio - Leadfoot
n Ravil Isyanov - Alexi Voskhod
n Isabel Lucas - Alice
n John Malkovich - Bruce Brazos
n Darius McCrary - Jazz
n Michael O'Neil - Tom Banachek
n James Remar - Sideswipe (11)
n André Sogliuzzo - Sideswipe (09)
n Keith Szarabajka - Laserbeak
n Rachael Taylor - Maggie
n Tony Todd - The Fallen
n Alan Tudyk - Dutch
n Rainn Wilson - Professor Colan
n Calvin Wimmer - Demolishor
n Jimmy Wood - Bonecrusher
n Michael York - Prime #1

d Bernie Mac - Bobby Bolivia
d Francesco Quinn - Dino/Mirage