The iPhone has seen some quality ports of old school fighting games recently, including a rather nifty version of Street Fighter IV. Back in the day, the biggest rival to Capcom's Street Fighter series was SNK's King of Fighters games, trading blows to see who could become the ultimate fight franchise. It's taken a while, but King of Fighters has now also been ported to the iPhone too.
The game is a 2D beat 'em up brimming with special moves and combos. Along with the usual punch and kick buttons, it also adds in an evade button and a 'special' button to allow you to dodge enemy attacks or execute blow out moves that stun your opponent. It differs from many of its rivals in that you pick three characters to form a team, each stepping in after the previous one is beaten.
Excellent visuals, great controls and surprisingly deep gameplay make this perhaps the best fighting game around on the iPhone at the moment.