New - February 2007 - Two new scenarios.
Both require soaked and wild expansion packs. ... Sorry there are no screenshots, for some reason I couldn't get them to save... hmm... anyway, After taking a few months off from playing RCT, I got back into it, played a few downloaded scenarios from other websites, a few good, but mostly they are complete parks with insane goals. These parks have plenty of room to build, and I had fun playing them. I hope you do too :)

JungleWorld - 5 separate parks to finish 3035kb
BlackHeart Park - dark and spooky themed 948kb

Four Corners 1,311 kb
Does not require Soaked or Wild expansions

Coaster Kingdom 1853kb dat file

RENAME A PEEP TO ACTIVATE THESE CHEATS

Cheat Codes are all case insensitive.
... you can often rename several peeps with the same name by varying the case like melanie warn and Melanie warn and melAnie warn

Beware; there is no confirmation on cheat activation - once you rename someone, its done.

Wild!:

Rabbit - Animals Constantly Breed - Should make your animals reproduce very quickly, like rabbits... unlike developers... !
Alvin Swazonegger - Allow Large Billboard Movies
Jurassic Dart - No idea
Soaked! and higher:
M Brookes - Enables you can place wall pieces and other scenery items on the edge of path tiles.
Alistair Lindsay - alters the speed at which some sound effects are played at pause, fast and fastest.
Rick Griffiths - changes the inside of a tunnel from rubble to sharks on both sides, the ceiling and the floor.
Mornington Crescent - This allows building shops etc underground (use SHIFT to lower an object's position until it is say, level with an underground path).
David Walsh - This allows removal of the user interface (ie all the icons, menus etc) using CTRL-U once the cheat is active. This is great for taking screen shots. Press CTRL-U again to get the user interface back.
v2 Final Patch OR Higher:
Isambard Kingdom Brunel - Trains Staff (Costs you about $1000 plus the total cost needed to fully train all of your Staff Members)
v1a Final Patch OR Higher:

Isambard Kingdom Brunel - Trains Staff (Costs you about $1000 plus the total cost needed to fully train all of your Staff Members)
FPS - Displays an Frames Per Second counter.
v1a Beta Patch OR Higher:

Ghost Town - Will stop the flow of peeps coming into your park. This seems irreversible and the only way to disable it is to shut down the game fully.
Andrew Thomas - decreases track friction, which can make coasters go faster along their tracks
David Braben - Disable the Lift Chain Speed & Launch Speed limits. Normally, you are not permitted over a set speed limit. Usage: Select a coaster. Select 'Operating Mode'. You must have 'Powered Launch' selected to alter the Launch Speed.
Andrew Gillett - Unknown effect (On the first Career mission, this code will double the value rating of your park - which will complete your first mission objective. On other tested missions, it seems to possibly cause a slight increase in park value too)
v1.0 Retail or Higher:

John D Rockefeller - Increase your money by $10,000
Chris Sawyer - Cheer (Lp) - All guests applaud you & Jump into the air
Mouse - They follow the mouse cursor. They start off looking at the ground because the cursor is at the bottom of the screen. Wave it around a bit and the peeps watch! (credit:mrbdamien)
Guido Fawkes - Enables the 'Advanced firework editor'. Usage: Scenery -> Firework Mixmaster -> Fireworks Displays -> Add firework display -> Advanced firework editor.
Atari - Cheer (Fade) - All guests applaud you
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 - You can also use CTRL-SHIFT-0 (the number zero) For more info click here .
A Hitchcock - Hitchcock - not sure what this does (could be related to the birds like Alfred's movie)
PhotoStory - unknown code
ATITech - Every Person (both guests & staff) move super fast, though the game time passes at normal speed (rides & coasters do not speed up) (Expires after 20 seconds)
Make Me Sick - All guests become Sick and vomit immediately (Repeat it to make the park insanely dirty - watch them handymen run)
Jonny Watts - PeepCam (see the world through the eyes of the guest who you just renamed)
Atomic - Causes 'nuke' shockwaves on coaster crashes.
Shifty - Makes the peeps dance
John Wardley - No Coaster Height Limit (ride & coaster tracks can be built without height limitations)
Frontier Unbreakable (Buildings/Rides/Coasters do not break down any longer)
Jon Roach - Ride All Rides (make all guests ride every parkride before leaving the park) OR, it may just make guests ignore their nausea rating
Sam Denney - Ride All Coasters (make all guests ride every park coaster before leaving the park) OR, it may just make guests ignore their nausea rating