I get them all the time.Your vision turns black and you have no idea what your doing for a few seconds.(Atleast that's what happens to me.)I think there pretty cool.
I had a couple times. Stand up on my computer to open the door since my mom is ringing the door bell..Walking walking.. boom im on the floor and I was like...wtf just happened? Vision was really dark while it happened. My mom quickly ran in and about to call 911 lol!
dude i get that all the time being baked and stand up i usually stand there or talk it off cause my eyes just black not much never been fully out cause of it
my gf has it was funny
I think they call that a "head ache".
But yea, blood rushes are a pretty cool feeling. I get them a lot when I drink something with tons of energy/caffeine in it.