This is the Schmidt Pain Scale. I heard about it on R4's "The Infinite Monkey Cage" earlier. I've only been stung by two of these.
I've shameless robbed it and updated it. Bet you can't spot mine.
1.0 Sweat bee: Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm.
1.2 Fire ant: Sharp, sudden, mildly alarming. Like walking across a shag carpet & reaching for the light switch.
1.8 Bullhorn acacia ant: A rare, piercing, elevated sort of pain. Someone has fired a staple into your cheek.
2.0 Bald-faced hornet: Rich, hearty, slightly crunchy. Similar to getting your hand mashed in a revolving door.
2.0 Yellowjacket: Hot and smoky, almost irreverent. Imagine WC Fields extinguishing a cigar on your tongue.
2.x Honey bee and European hornet.
3.0 Red harvester ant: Bold and unrelenting. Somebody is using a drill to excavate your ingrown toenail.
3.0 Paper wasp: Caustic & burning. Distinctly bitter aftertaste. Like spilling a beaker of Hydrochloric acid on a paper cut.
4.0 Pepsis wasp: Blinding, fierce, shockingly electric. A running hair drier has been dropped into your bubble bath (if you get stung by one you might as well lie down and scream).
4.0+ Bullet ant: Pure, intense, brilliant pain. Like walking over flaming charcoal with a 3-inch nail in your heel.
5.0 Knowing that you can never be mine.