Denis Leary/YMMV

Acceptable Targets: The Douchebag Song is basically one long string of these, including the PC Police, people who text while driving and walking, people who wear sandals with socks, white people with dreadlocks, people who bike instead of taking the train, the immigration police in Arizona, Glenn Beck, Al Gore, the cast of Jersey Shore, The Lohan Clan, the Kardashians, and others.
Crosses the Line Twice
Crowning Moment of Heartwarming: Shortly after his son was born he ended a performance with a monologue about how he wanted to leave his son the best world he could. Subverted two seconds later with "But sometimes I think, ah, fuck 'im."
Dude, Not Funny: An out-of-context remark about people mis/overdiagnosing autism and/or using it as an excuse for poor performance did ruffle a few feathers. But he apologized about it.
Ear Worm: "I drive really slow, in the ultra-fast lane, while people behind me are goin' insane... I'm an ASSHOLE!"
- Douchebag Song may be even worse.
Memetic Mutation: His closing line on most of his MTV promos:

"I think you hear me knockin', and I think I'm comin' in."