I spend a LOT of time outdoors. Hiking, camping, backpacking. I've been stung so often and by so many flying insects that a lot of types for a long time began not to bother me too much. With the exception of large hornets. One day some years back I was sitting out eating a sandwich at the picnic table in our yard. As I was sitting there minding my own business, this enormous hornet landed on my right forearm. I decided to just hold still and not do anything to upset it, and suddenly it stung me, for no reason I can say. The pain was hideous and my forearm swelled tremendously around the sting area. I have to say it was the most painful sting I have suffered (and I have suffered dozens). I hope never again to be stung by such an insect.
The only other thing that came close to that kind of pain from a sting was when, as a teenager, I rolled over on a common scorpion as I slept. My right shoulder was crushing him, so the scorpion had tremendous opportunity to fill me with its poison. I'd been stung by these common scorpions before, but never like this. The sting area was so full of poison that over the following weeks the wound crusted over and dead flesh crumbled off like dried paper. Yes, it was pretty horrible.
But as far as bees and yellowjackets and common wasps...it hurts when I get stung by them, but I barely acknowledge it.
One thing I definitely want to avoid, though, are those huge red wasps that we have down here in the South. I've yet to be stung by one, and I'd like to keep it that way.