For items, @give Username/ID/Amount
For vehicles, @vehicle Username/ID
For animals, @animal ID
For experience, @experience Username/Amount
For teleporting, @teleport Username/Location
For controlling time, @day, @night, @time Value
For controlling the weather, @weather none, @weather storm, @weather blizzard
For calling in an airdrop of supplies, @airdrop
For changing your reputation around, @reputation Username/Value
Note, as of 3.14.13.0, "/" can now be used for commands as well as "@"
