Not to start a huge riot here, but MP, depending on the RPG could mean either Mana or Magic Point.
http://en.wikipedia.org/wiki/Magic_point
The screen cap at the right of the page is Final Fantasy Tactics.
Although either could be correct, it just depends which RPGs you grew up with.
Magic points (MP) are units of magical power that are used in many role-playing, computer role-playing and similar games as an expendable resource that is needed to pay for magic spells.
http://en.wikipedia.org/wiki/Magic_point
The screen cap at the right of the page is Final Fantasy Tactics.
Although either could be correct, it just depends which RPGs you grew up with.