Attack Reels is an Overdrive used by Wakka, who spins the slots with various attack multipliers (1 Hit, 2 Hit as well as a Miss slot). The stopped multipliers determine how many attacks take place; for instance, if Wakka lines up 1 Hit, 1 Hit, 2 Hit, he would attack random enemies four times. If the symbols lined up match, the attack is doubled; e.g., three 2 Hits will attack 12 times (6 attacks x2).
In the initial releases, Attack Reels was potentially the most powerful attack, usurped only by Anima's Overdrive in the PAL, International, and HD Remaster versions. It appears as a prize in a blitzball league.