Little Guitars is a song by Van Halen. It is one of the harder songs in Guitar Hero Van Halen, mostly for the intro.
While not nearly as difficult as some songs in the final tier (Spanish Fly, Eruption, I'm the One, etc.) Little Guitars is notorious for it's intro; a flamenco-style, one minute acoustic guitar solo. It starts simply, then begins rapid speed picking; imagine the notes as the reverse of the Hangar 18/Holy Wars/Welcome Home (Sanitarium) chart. Instead of holding the low note and fretting the high notes, you have to hold the high note and release to hit the alternating low notes, making a difficult section to sightread.
The song itself is far easier, but can catch amateurs out with it's tricky, rapid-fire chord structure.