Zoo Tycoon 2

Africa
Put a fence around the entrance to the zoo so that the entire zoo qualifies as a cage. Then, cover the whole zoo in savana grass and add plants and lakes. Place some animals then walk around as a zoo keeper/guest. To do this faster, do not get staff, food/water dishes or shelters. It will look unnatural. If you put gazelles in a pack, only put about two to six of them or some might ditch the pack. If you encounter across a dirty animal, wash it or all the animals will get sick and die. Note: Plant eaters will get eaten.

Flower Arch
Finish all scenarios in Troubled Zoos campaign.

Flowerpost
Finish all scenarios in Zookeeper in Training campaign.

Free trees and other stuff
When you are in any zoo mode (campaign, challenge, and freeform) most zoos should have already existing trees(and occasionally things like flower beds, benches, etc.) at the start. All you have to do is left click the item you want and move it to where you want it.This saves money when you are on a tight budget and is really easy.

Gilded Panda Statue
Finish all scenarios in The Mysterious Panda campaign.

Globe Statue
Finish all scenarios in The Globe campaign.

How to walk faster
With your mouse you can move in guest mode. Its kind of slow so hold down SHIFT and you will then walk faster!

Jungle and African themes
You need to complete five photo safari challenges and five game challenges to unlock them.

Make people repay to enter zoo
To make people repay to enter zoo simply pick them up and put them outside the gate and they will repay. Note if someone is leaving your zoo and you do this they will not come back in and they will walk out.

Mysterious Panda Campaign
Finish all scenarios in Conservation Programs campaign.

Recycle bins
Maintenance workers do not pick up recycle bin trash. You must do this yourself.

Secrets
Run in Zoo Guest Mode and Photo Safari Mode: Since left-clicking the mouse makes you walk in Zoo Guest and Photo Safari Mode, and so does W or Up, you can walk twice as fast (aka run) by holding two of these.

Sundial Statue
Finish all scenarios in Prevent Animal Abuse campaign.

Walk twice as fast
Run in Zoo Guest Mode and Photo Safari Mode: Since left-clicking the mouse makes you walk in Zoo Guest and Photo Safari Mode, and so does W or Up, you can walk twice as fast (aka run) by holding two of these.