Beyoncé's had a little help on her way to world-conquering stardom. She's assembled an all-star crew of collaborators that includes both household names like Kanye West and underground kings like Bun B. But she can be choosy when it comes to her own guest spots. Bey only lends her royal voice to fellow superstars like Lady Gaga, Alicia Keys, and the man who finally put a ring on it.