I do have a couple:
-You can remove the entrance/exit from a ride after it has been opened. Removing the exit behaves differently depending on the ride:
On tracked rides, guests are stuck and will never get off.
On flat rides, guests will just walk off the ride platform after riding.
If you delete a ride with no exit while guests are riding. The guests will be teleported to the map's origin (0,0)
You can make the smallest ride in RCT3 that guests can use with this method for the Crazy Golf.
-A really cheaty way to beat scenarios is to import designs from RCT1/2 since importing rides completely bypasses research.
-You can trap guests by using a lot of entertainers in a small area. Guests will get caught in a loop of watching them.
-In the scenario editor, you can offset the skybox by subtracting one edge of the map and add to the opposite side.
-You can get negative stats for the Aquarium by repeating the same piece over and over again.
All types of animal shows that use mixmaster can also get negative stats by making them too long.
-Dizzy Dropper has no friction.
-Like the older games, RCT3 has stat penalties for not making the minimum stat requirements, however RCT3 does not have any excessive G-force penalties.
-In the base game, hiring staff in sandbox mode will not make them fully trained.
-If you were to import a design from OpenRCT2 that uses the new color palette, the game will crash.