The Philadelphia area has some "stellar" local commercials - past and present.
The Krass Brothers ones are probably the most remembered. They used to air at the cheapest times on the cheap-o UHF stations and were normally only 7 seconds long. The neat part is that they'll make as much sense to you non-Philly people as they do to us...which is about ZERO.
Commercial 1 (YouTube)Commercial 2Commercial 3Commercial 4Commercial 5Interesting little
bio-page (link) on the dude in the commercials. Funny line, "His last wish was to have a plaque inscribed, 'He went in a Krass Brothers suit.' He did."
This one here, though, is a genuine classic. I won't say what it is, but this commercial ran unchanged (!) for 15-20 years. Unfortunately, I cannot find video of the commercial, but in this case, the song will do just fine.
This is a link to an MP3 of the song (right-click/save-as).
If you're not from the Philly area, just dig the catchy tune...but if you are, be prepared to be mind-warped back into the 1970's or 80's, depending on when you were watching WPHL-17.

. There is a pretty
cool site (link) dedicated to that business that you may find of interest.
As for a commercial I can remember absolutely hating? Nothing beats this one on the Annoy-o-meter:
Encyclopedia Britannica commercial (link). I used to swear that if I got a hold of that kid, the crime scene detectives would be "wondering where his mandibula is".

. Yikes...it appears that kid actually had a semblance of a career...heh...
IMDB (link). No wonder he was/is a mess..."He was known only as Baby Boy until he received his name on his fifth birthday". Geez.