Frontier = All rides and coasters never break down Guido Fawkes = Gives access to the advanced Fireworks editor
Sam Denney = Peeps ride all coasters
Jon Roach = Peeps ride all non-coaster rides
John Wardley = Removes height restrictions when building coasters
Chris Sawyer = Guests Jump for joy
Atari = All guests Laugh
David Braben = Unlimited launch and chain lift speeds (only works after update #1)
Andrew Thomas = Decreases track friction, which can help when importing some RCT1 or 2 coasters into RCT3. Only works after Update #1.
John D Rockefeller = Gives you $10,000
James Hunt = You are given a buggy vehicle to ride in - exit coastercam and delete as scenery when done.
D Lean = Open the "Flying Camera" routes editor
Mouse = All guests stand around looking down at the ground
ATITech = Every Person (both guests & staff) move super fast,
Make Me Sick = All guests become Sick and vomit immediately
Jonny Watts = PeepCam (see the world through the eyes of the guest who you just renamed)
Atomic = Big Explosion - makes a huge explosion on a coaster crash
Simon Foster = Pains Pictures of Rides
Melanie Warn = Increases Guests' Happiness
Katie Brayshaw = Waving Guests
FPS = Shows Frames Per Second
Andrew Gillett = Reduces friction to none on all rollercoasters
hope this helps 
