What are your favorite mashups?

That The Knack/Ting Tings/Toni Basil mashup got me thinking about other great mashups, so I'm wondering what your favorites are. Here are a few of mine:

• This Green Day/Collective Soul mashup is just one of the best, most seamless I've heard.
• Kind of like the funny ones, and this Taylor Swift/NIN mashup makes me giggle
• My all-time favorite, because it's both really well done and is hysterically funny to me, has to be this The Wiggles/Slipknot mashup