Bonus Totems: Find the following totems to open up multi-player bonuses:

Yellow Ant
Location: Goldwood
Character: Vela

Blue Ant
Location: SS Anubis, Generator Room 2F
Character: Any

Red Ant
Location: Ichor, Military Base
Character: Juno, Lupus

Green Ant
Location: Spawn Ship, Cargo Sewer
Character: Any

Male Tribal
Location: Sekhmet, Channel Area
Character: Any
Requirements: Magenta Key 

Female Tribal
Location: Rith Essa Mine
Character: Vela
Requirements: Mine Key 

Zombie Termite
Location: Tawfret, Treehut
Character: Lupus

Beetle Termite
Location: Tawfret, Lost Tomb
Character: Vela

Metallic Termite
Location: Sekhmet, Spiral Walkway (hover across)
Character: Lupus

Purple Termite
Location: Mizar's Palace
Character: Juno

Extra Stages
Rith Essa Mine Stage
Location: Walkway (station)
Character: Any
Requirements: Powered-up

Tunnels Stage
Location: Rith Essa, Waterfalls
Character: Vela

Space Station Stage
Location: Space Station, Basement
Character: Any

King of the Hill
Location: Cerulean Holding Room
Character: Any

Cyborg Ant
Location: Various
Character: Floyd
Requirements: Get an 'Expert' rating on all Floyd Missions

Goldwood Target Range
Location: Goldwood
Character: Floyd
Requirements: Get Gold on Goldwood Floyd Mission 

Rith Essa Target Range
Location: Eschebone
Character: Floyd
Requirements: Get Gold on Eschebone Floyd Mission 

Jeff & Barry Arcade Racing
Location: Ichor Arcade
Character: Any
Requirements: Come in first on Jeff & Barry Arcade Racing 

Jeff & Barry Arcade Racing II
Location: Ichor Arcade
Character: Any
Requirements: Come in first on Jeff & Barry Arcade Racing II 

Greenwood Village Race Track
Location: Ichor Arcade
Character: Any
Requirements: Break the top records on both Jeff & Barry arcade machines. 

Mizar 3D Racer
Location: Mizar's Palace
Character: Any
Requirements: Win the Mizar races. 

Rainbow blood:
Collect 100 ant heads to enable Rainbow Blood in the 'Cheats' menu.

Jet Force Kids:
Collect 200 ant heads to enable this in the 'Cheats' menu. 

Ants into Pants:
Collect 300 ant heads to enable this cheat in the 'Cheats' menu.
It turns all the enemy drones into stick figures with big pants.