In Uno, can you play a Wild Draw 4 Card when you have another Wild Card in your hand?
According to the rules sheet from Mattel:


  You may only play this card when you do NOT have another card in your hand that matches the COLOR on the DISCARD pile (but it is acceptable to play this card if you have matching number or Action Cards).


Since Wild cards are classified as Action cards, you are legally allowed to play a Wild Draw Four when you have a Wild in hand.