The Maximum Power Kamehameha is Master Roshi's signature attack, the Kamehameha Wave, he uses in his Max Power form. This is just like the normal blast, but when Roshi is in his Max Power form, he can increase the Kamehameha to its maximum potential, inflicting even greater damage than the normal Kamehameha (hence the name "Maximum Power Kamehameha").
The attack was named in the Budokai Tenkaichi series and is Master Roshi's Ultimate Blast in his Max Power form.
History and usage
Goku and Chi-Chi brought Master Roshi to Fire Mountain to extinguish the roaring flames on the Ox-King's castle so that they could obtain a Dragon Ball. Master Roshi transformed into his Max Power form and launced the Maximum Power Kamehameha for the first time. The Maximum Power Kamehameha suceeded in extinguishing the fire, but the blast was so powerful that it blew away the mountain and castle.