A match that can only end when one wrestler verbally says 'I quit' into a microphone. No pinfalls, no submissions, no ref stoppage. Just pain until someone breaks. The drama is entirely psychological — it's not about the moves, it's about the breaking point. The Rock vs. Mankind Royal Rumble 1999 is the most famous (and most controversial — they used a recording of Mankind's voice). John Cena has had some of the best modern I Quit matches because his character never gives up.
"The ref is shoving a microphone in his face. 'Do you quit?' 'NEVER!' He just got hit with another chair shot. 'Do you quit?'"