For a brief time early in this poker thing, I tried for the Intimidator look. (If you count the cards, you'll see that we Intimidators play a man's game: five-card draw. We take our whiskey straight up, too.) After only a few sessions, I decided that I looked, well, a little silly. Since then, I go for the Allen Cunningham effect--just shut up and try to blend into the background so nobody notices me. It seems to work OK, and fits my natural personality better than trying to scare people by appearance alone. At 5'7" and 145 pounds, I don't exactly have the hulking ferocity of, say, T.J. Cloutier, of whom James McManus wrote, "While there's nothing overt about it, the man comfortably embodies a lethal threat, even from the seated position. If it happens to suit him, he can reach across the table and rupture key vertebrae with his bare hand, and everyone sitting here understands this down in our helical enzymes." Positively Fifth Street, p. 237.
I wonder if a big check-raise coming from the most harmless-looking guy at the table--one you were barely even aware was there--is actually scarier than one coming from a player who looks like he's trying to frighten you out of the pot.