The combination of hip-hop or rap and classical isn't as rare (or as odd) as you might think!
Nas
"I Can" samples Beethoven
"Für Elise".
Coolio
"C U When U Get There" samples Pachelbel
"Canon In D".
Robin Thicke
"When I Get You Alone" samples Beethoven
"5th Symphony". (Okay, really it samples Walter Murphy
"A Fifth Of Beethoven," which samples Beethoven's 5th.)
Ludacris
"Coming 2 America" samples both Mozart
"Dies Irae" and the fourth and final movement of Dvorak
"Symphony No. 9 In E Minor, From The New World" (commonly referred to as the "New World Symphony").
Kelis
"Like You" samples Mozart
"Queen Of The Night".
Beastie Boys
"Intergalactic" samples Stravinsky
"The Rite Of Spring".
The Rapsody featuring LL Cool J
"Dear Mallika" samples Delibes
"Flower Duet".
That's a good start to the list! Can anyone think of any others?