Gosh, so many good step workouts.
But the ones I reach for most are Amy Bento ASC 2 and 3. I also like most of Cathe's (I might be an outlier in that I didn't really like Rhythmic Step). Also like Christi Taylor. Over the past year or two I've gotten more into complex step, and just arranged a trade for a Seasun.
If I had to save one step workout from a pile of rubble, it would probably be ASC 3.