Excluding the questionable sanity of the Lion Totem Barbarian substitution, I've found that Pounce can be had by only a few means. The +1 LA Catfolk race (from Races of the Wild) has exclusive access to Pounce at first level, but only against flatfooted opponents (a serious limitation at any level, somewhat mitigated because the catfolk get +4 Dexterity for +2 Initiative). At 4th level a psychic warrior can learn to manifest Psionic Charge, a 2nd-level swift-action power. A druid can use the Lion's Charge wild feat to expend a daily wild shape use (ouch!) for just a single pounce. Alternatively, a druid could wild shape into something with Pounce as one of its extraordinary abilities.
And I'm pretty sure that's it. If you can manage one of those, you can combine Leap Attack with pouncing for lots and lots of offensive capability. You don't need 6-to-1 power attack ratios to make such a build very nasty. The 3-to-1 you get is pretty nasty by itself.