I noticed that Violent submitted "Dammit" by Blink-182 as a pop punk song, but I think that there are other songs that would better represent the genre. I think bands such as Screeching Weasel, Teenage Bottlerocket, Dillinger Four, The Queers, and Lagwagon represent the genre well, and maintain the punk part better than Blink-182.
These are what I have in mind:
YouTube - Dillinger Four - A Jingle For The Product
YouTube - Screeching Weasel - Cool Kids
YouTube - Lagwagon - Violins
YouTube - Radio - Teenage Bottlerocket
YouTube - The Queers - Ursala Finally Has Tits