Thunderhand is a move used by Luigi during the events of Mario & Luigi: Superstar Saga. It is also the brother move of the Firebrand. He is taught this by the Thunder God in the Thunder Palace. It is even further advanced after Merri teaches him how to use it along with Mario.
Thunderhand can power Lightning Orbs and defeat thunder-prone enemies. It was the only way to defeat the Piranha Plants that cover the runway on the Beanbean International Airport. In battle it proves useful against certain enemies. They can also use Thunder Bros. after the Jellyfish Sisters teach Luigi the advanced method. After the advanced method is taught, Luigi can tickle Mario causing them to "stick together" and move slower. This can be used to pass through slow-moving spiked barrels and activate Boo Statues.