I use the two altissimo notes I can reach (G and A on tenor) and whenever I think it would be a good idea to learn a few more fingerings, e.g. G# seems to want to be played, I cannae be ersed to put down the sax, go to learned tome or computer and look it up
I recently listened to a musician going over a (pink) Selmer MK VI for his own interest in the techs workshop. This chap played note-type notes but he also breathed sub-tones, spread harmonics, fashioned multitones, pushed altissimo notes and generally explored the nooks and crannies of the instruments abilities... I came away thinking that these skills do not just add seasoning to ones performance but may also improve the handling of the ordinary notes
Spurred by this and other sources (a member, name begins with a Zed (Zee), some time ago espoused the technique of reaching altissimo with ordinary fingering via harmonics) I've been experimenting with noises, sqeaks and notes with whatever technique occurs to me... it's fun and who knows might be useful?
I really should learn some fingerings though