I think the biggest culprit of influences rubbing off is when writing balads. There's something about the Canon chord progression, or at least a variation, that seems to sound great when going for them searing heartfelt vocal-lines and solos. I've heard countless bands use it, but all to a different degree to make it sound unique. But essentially everyone has nicked it of Pachabell. But again, chord progressions are one thing. Actual structured riffs are a bit harder to mimick, but it still crops up in peoples playing. Blues licks especially