cyborg8274:
NO, i haven't. I'm still learning and there's no need for sarcasm. You could just not reply at all and someone else who's more polite will surely help.
If you Google "TIP120 Arduino" (as I did) you will find loads of circuits showing a TIP120 connected to an Arduino digital pin. That way you would have had your answer much quicker, without waiting for anyone here.
If you want an even more direct answer...yes you need a resistor. The value will depend on what it is that you are switching.
Steve