Base-Breaking Character: Sedrick, particularly after he went trigger-happy and tried to take out the entire Garrott family. According to the author's tumblr, that arc cost her about a third of the readership.
greyliliy: But no, Sedrick going Axe-Crazy lost me like 300 readers. WaM officially has a base-breaker.
Foe Yay: Wiglaf and Azrael, at least in Mordred's mind. First spotted in the Orb of Bliss arc when he says "maybe he thinks you're cute" when Azrael turned up also looking for the orb. More recently, he teased Wiglaf that Azrael was his "boy toy" when he said that they might need Azrael's help.
Probably the first instance was here with Wiglaf's last line, which is even funnier when you realize what he actually said. He said 'Forgive me dearest/sweetheart And then let's not forget this infamous scene.
While it's Wiglaf taunting Driver, the last word bubble on this page is bound to get the fans going.
And Herschell taunting Wiglaf here about Mordred. And even before that, just the way he spoke to him.
Squick: Ever wonder why Azrael shows no interest in women, or men, for that matter? He was castrated for medical reasons, possibly early onset testicular cancer. Remember, once you read that spoiler, you can never unread it. You have been warned.