The Bass Saxophone is the original saxophone; the instrument upon which Adolph Sax developed the rest of the family. It should be treated with more respect. In some regards it can be thought of as a larger version of the Baritone Saxophone. It has a heavy voice and is far more ponderous than the other saxophones mentioned so far. Most often, the Bass Saxophone will be an older instrument built in the days of the saxophone crazy of the 1920s, though modern instruments are extant.
Many instruments, both older and modern, only ascend to a keyed E-flat above the staff, though notes above this are possible through the use of harmonics. That said there is really not much use in keeping the Bass Saxophone in its high register.
I once used the Bass Saxophone in a work where I had it depict the voice of a noble, powerful, and terrible king. I can think of no other instrument that can convey this. There is a somber sound throughout its range.
Its low notes are organ-like and resonate and can provide a powerful foundation for the entire woodwind section. It is a shame that the Bass Saxophone is not seen more often. Surprisingly, it is scored for in many works published before 1950, but very few after.
There seems to be only one surviving playable Bass Saxophone in C left in the world. I linked to the video of it in the saxophone introduction page.
van Dijk Concerto for Bass Saxophone
Chanson Triste by Koussevitzky
A song by Grieg