I have seen lots of undercutters so far and I have also seens lots of different styles of undercutting.
Offhand, I could mention the "Bot", the "Undercutter on a timer" and the "Casual".
Yesterday I encountered for the first time the "no lifer" type.
This guy does nothing all day other than being in Ironforge and undercutting auctions. This is amazing, I have never seen this type before. I first noticed him when he undercutted a market I shared with one Bot and started to monitor him.
He first undercutted me at 10:30 in the morning. I kept coming back every half an hour or so for 2-3 hours undercutting him back, then logged out. When I returned to the game at 5pm or so he was still there in Ironforge alright, and "active" not "away". I did other things with my toons, raided, did dailies, dungeons etc and kept coming back whenever I could to UC him. Long story short I must have undercutted him around 20 times, always to be re UC by him within seconds. Out of curiosity I logged in yesterday at 3:30 am and sure enough he was there.
This guy is amazing, he like a soldier on duty or a pro on a farming schedule. Always sitting in IF UC and posting auctions, never participating in the game in any way. He does nothing other than play the AH.
I wonder how you deal with this guy.