McDonald's has some of the worst ones ever, indeed. Of course one that pisses me off even more than that are the herpes medication ads that immediately start in with "Living with Genital Herpes...." While I'm eating! In the middle of it! No warning, no chance to change the channel, just instantly cut to, "my vagina has things living in it, BLAAAAAAHHHHHHH!!!!!!"
There's a local-ish loan company called the Dollar Loan Center here. They ran a radio spot with a guy singing about how he bet his rent money on the Raiders and lost, which was followed by the announcer saying, "if your only gambling problem is not having enough money...." Not much offends me, but that was sure one thing that did it.