There are a plethora of ways to obtain gold coins in Super Mario 3D World. One of the most interesting is the Gold Shell. This helpful item gives Mario or your favorite character a whole mess of coins, but it also comes in handy for destroying enemies. Give the shell a kick and watch it ricochet throughout the environment. You can even hop inside and go for a ride.
On that note, this video breaks it all down. Whoo-hoo!