Yes, buff is a Scrabble word!
...and is worth 12 points in Scrabble, and 14 points in Words with Friends
buff
Verb
1. Strike, beat repeatedly
2. Polish and make shiny
Adjective
1. Of the yellowish-beige color of buff leather
Noun
1. An ardent follower and admirer
2. A soft thick undyed leather from the skins of e.g. buffalo or oxen
3. Bare skin; naked
4. A medium to dark tan color
5. An implement consisting of soft material mounted on a block; used for polishing (as in manicuring)
What Scrabble words can I make with the letters in buff?
3 Letter Words