Gear Fourth!

In this form, Luffy’s Busoshoku Haki takes the shape of tribal flames on his body. This is the first example of Busoshoku Haki forming a recognizable pattern.
The position of Luffy’s hands to perform Leo Bazooka highly resembles the Kamehameha stance from the Dragon Ball series, a manga that highly inspired Oda.
Similarly to Gear 2nd, Gear 4th allows Luffy to use techniques that appear to be his own reimagining of Rokushiki abilities, his pseudo-flight bears a striking resemblance to Geppo, and Leo Bazooka is seemingly reminiscent of Rokuogan (with Gear 2nd allowing Luffy to move at a speed similar to Soru)

ONE PIECE GOLD