What music do you use to assess your system?

I'm looking for music that will reveal shortcomings or strengths within ones system. Lets list some of our favorite songs that have: good, fluctuating bass lines, songs that have a solid, centerd vocal, songs that are super complex with alot going on, songs that test tone, songs that test inner and micro detail, songs that test how well a speaker can convey dynamic swing, and any other aspects I didn't mention.

Of course I'm not looking for one song that covers all areas, I'm fine with one song only covering one aspect.

When listing songs, please include what we are looking for in that particular song!
I like to use the opening of the vinyl LP Genesis, A Trick of the Tale. It has a nice, broad range of notes. Bad, digital listen here: http://www.youtube.com/watch?v=kJIVuinJlsU

I'm such a gear head that I don't actually use music to assess my system. I use many other criteria though, such as; looks, cost, number of knobs and believe it or not weight. I figure the more something weighs the more stuff is in there so it has to sound good. Oh yeah, where you buy a component is also important. 8^)
I don't "assess" my own system, but when I am auditioning components, I usually use these: Something off Brubeck's Take 5 record. Desmond's alto will show up a honky or forward midrange like nothing i've heard. Nora Jones Feels like Home. Music isn't the greatest, but her voice is very well recorded and up front. Will also expose midrange and vocal forwardness and lack of naturalness. James Taylor JT. Vocals reach down to the baritone range and and will expose a tubby or thin lower midrange. This is often a function of the room, but it's still a useful tool. Lambchop Is a Woman - great low-level sounds like piano pedal and fretboard sounds show a system's ability to reproduce little sounds. That's pretty much what I go by.
I try to take something that has very complex piano parts - Yelenna Eckemoff's Cold Sun comes to mind - because in my experience a system that reproduces a piano well - with all of its subtlety-to-bombast and everything in between - can do just about anything I'm going to want it to do. Very difficult instrument to reproduce truly well.