Unlock All Items:
Hit 30 Barrels during Challenge 7 to unlock all items.
Unlock All Worlds:
Find the Hidden Key in Challenge 18 to unlock all worlds.
Hit 50 Barrels during Challenge 18 to get Unlimited Ammo.
Hit 179 Barrels during Challenge 17 to get Unlimited Health.
Get 8 Zappers during Challenge 4 to get Unlimited Turbo.
Unlock All Cars:
Hit 11 Bonus Stunt Items while completing Challenge 8 to unlock all cars.
Upgrade your Laser:
Finish Challenge 18 on Very Hard Difficulty to upgrade the Laser.