Rainbow Blood mode:
Collect 100 ant heads to unlock the "Rainbow Blood" option on the cheat menu.

Ants Into Pants mode:
Collect 300 ant heads to unlock the "Ants Into Pants" option on the cheat menu. Enable this option to get stick figures with large pants as enemies.

Collect out of reach gems:
Shoot gems that are out of reach to bring them within range.

Jet Force Kids mode:
Collect 200 ant heads to unlock the "Jet Force Kids" option on the cheat menu. Enable this option to unlock the kid version of the game's characters.

Hover with jetpack:
Press C-Down to hover with the jetpack. Note: This consumes less fuel then actively flying.

Refill ammunition:
Switch to the shotgun, pistol or machine gun if running low on ammunition and run over the bodies of dead enemies to collect more bullets for that weapon. To refill the flame thrower, shoot Tribals once to force them to drop their lanterns without killing them. Collect the lanterns to use as flame thrower ammunition.

Quick character change:
Press C-Left or C-Right at the map screen to quickly change the character icons.

Hear Lupus howl:
Press C-Down when playing as Lupus

Bonus deathmatch characters:

Play as Yellow Ant:
Make contact with the hidden Totem Pole as Vela in Goldwood.

Play as Blue Ant:
Make contact with the hidden Totem Pole in SS Anubis (Generator Room 2F).

Play as Red Ant:
Make contact with the hidden Totem Pole as Juno in Ichor (Military Base).

Play as Green Ant:
Make contact with the hidden Totem Pole in Spawn Ship (Cargo Sewer).

Play as Male Tribal:
Play as Lupus and collect the Magenta Key in Eschebone (Thorax. left intestine). Then, make contact with the hidden Totem Pole as Lupus in Sekhmet (Channel Area).

Play as Female Tribal:
Collect the Mine Key. Then, make contact with the hidden Totem Pole as Vela in Rith Essa (Mine).

Play as Zombie Termite:
Then, make contact with the hidden Totem Pole as Lupus in Tawfret (Treehut).

Play as Beetle Termite:
Then, make contact with the hidden Totem Pole as Vela in Tawfret (Tomb).

Play as Metallic Termite:
Make contact with the hidden Totem Pole as Lupus in Sekhmet, (hover across the Spiral Walkway).

Play as Purple Termite:
Make contact with the hidden Totem Pole as Juno in Mizar's Palace.

Play as Cyborg Ant:
Obtain an expert rank as Floyd on all Floyd levels

Bonus multi-player levels characters:

King of the Hill:
Make contact with the hidden Totem Pole in Cerulean Holding Room.

Tunnels:
Make contact with the hidden Totem Pole as Vela in Rith Essa Waterfalls.

Rith Essa Mine:
Collect powered jetpacks. Then, make contact with the hidden Totem Pole in Walkway Station.

Space Station:
Make contact with the hidden Totem Pole in Space Station Basement.

Goldwood Target Range:
Obtain a gold rank on the Goldwood Floyd level.

Rith Essa Target Range:
Obtain a gold rank on the Eschebone Floyd level.

Jeff And Barry Arcade Racing:
Obtain a first place score on Jeff And Barry Arcade Racing at Ichor Arcade.

Jeff And Barry Arcade Racing II:
Obtain a first place score on Jeff And Barry Arcade Racing II at Ichor Arcade.

Greenwood Village Race Track:
Obtain a first place score on both Jeff And Barry Arcade Racing machines at Ichor Arcade.

Mizar 3D Racer:
Obtain a first place finish in the races at Mizar's Palace