As far as other figures that are tough to find, aside from the surprising core characters that are disappearing, it is much the same as other areas. The Tarkin wave (#45-47) hasn't shown up here yet, as far as I know, so this is from #1-44.
Royal Guard - Red (never seen one on the pegs at any of the "Big 3" retailers)
Royal Guard - Blue (seen once since opening day, but not anymore)
Clone #41 - Haven't seen at retail yet, got a couple online.
Clone #6 - All disappeared now, could find them now and then earlier though.
Tank Gunner - Saw them a couple times at Target, but they aren't anywhere now.
Clone Commander - Started to show up in larger quantities at Wal-Mart, but they've all disappeared as well.
Darth Vader - Haven't seen this figure anywhere for awhile either.