Not yet, but I was very close to faint once.
I was like 11, I don't remember, but my parents took me to one of those markets that are in the open and have a wide variety of stuff to buy and it was cheaper than other places. It was a hot day and I had been walking with them for hours, before we left, we went to one of the few places that weren't in the open to buy some meat... we had to wait in a long line to buy... and the smell of fish in there was killing me, lol... I started to feel bad in there and my vision was starting to get all clouded like when you have low blood pressure or something.
I just tried to hide it and pretended nothing was wrong with me... I didn't say anything... we then got out of that smelly place and went back outside because they said they had to buy one last thing before getting back in the car to leave...
By that time, I almost couldn't see anything anymore but I just kept walking without looking in front of me... I just looked at the ground. I couldn't keep my legs straight anymore, with each step I took, when I put my foot on the ground, my knee would give in and my leg would flex a little and had to make some effort to put it straight and make the next step.
My dad noticed I was walking weird and he was like "wo-haw!, wo-haw!, careful not to fall there buddy!" in a joking tone but my mom was like "Grab him!, don't you see he's going to fall!? he's not playing!" so he grabbed me and took me in his arms back to the car, bought me something to drink and left me there with my mom while he went to buy whatever was left to buy and then we left. I recovered like 5-10 minutes after sitting in the car, it was no big deal.
That time was the closest I was from fainting.