ENFP type 8 sp/sx.
I usually get around 8 hours a night.. I can deal with 6-7 just fine, I'll just be a little groggy when I wake up. These are my preferences though 6-8.
I function on any amount of sleep, or a lackthereof, depending on the importance and intensity of what I'm doing.
If I sleep 9-10 hours I don't feel much more rested, but sometimes I want the luxury of not waking up to an alarm and this is usually the amount of sleep I get when I do that.
I've also functioned just fine on 2-3 hours of sleep. Anything more than 3 hours and less than 5 hours I feel like crap when I wake up.