Hadouken is a blue fireball that Ryu and Ken can perform in the Street Fighter series. Various characters in the series have attacks similar to Hadoken.
Super Smash Bros. for 3DS and Wii U
Hadouken is Ryu's standard special in Super Smash Bros. for 3DS and Wii U. It can also be performed using the usual input used in the Street Fighter games. Using this input will create a bigger fireball with slightly more damage.
Ryu can also input the Shakunetsu Hadoken using the input for Yoga Flame; back, down back, down, down forward, forward, attack/special. The red fireball is a multihit move that in the end does a bit more damage but, it has weak knockback and the fist hit doesn't flinch.