Firstly, if you want to talk about a band GET THE NAME RIGHT! It's Yellowcard, not Yellow Card, despite their logo being a crossed Y and C. Edit the title of the thread, please.
Now that I've got that off my mind, yes, Yellowcard rates highly among my favourite bands. I like the extra touch that Sean's violin adds to the pop-punk, especially as I play violin myself. My favourite song by them is "Only One", although I'm also quite addicted to "Back Home".