The 2000-P "Wounded Eagle" Sacagawea Dollar is so-named because of a raised die flaw that cuts across the eagle's belly (see the attribution image above). As of January 2012, this variety remains elusive, with PCGS showing a population of 115 examples in all grades. As more collectors examine their coins, the population may rise, or this could turn out to be a very scarce variety. Time will tell.
The vast majority of the known examples are Mint State, usually in MS-64 to MS-66. The finest examples are five PCGS MS67s.