Does "air stroking" count as a weird and useless affectation?
Wrapping a paper towel around the stick in the bridge hand. This actually works pretty well but looks goofy.
Bill Hawkins was a top US 3-C player. He played side spin with a lot of swoop across the ball.
I'd put slip stroke in the weird and useless category, but others seem to like it.
Holding a piece of chalk at all times in the bridge hand. Lou Butera use to do this for speed.
Using inside english on nearly every shot. A friend of mine said it was much easier to aim shots like this. Of course, position suffers.
As noted above, I have also seen a player who intentionally looked anywhere but at the table when seated. I've been tempted to do that for opponents I just can't bear to watch, and maybe that's why he did it, but it is also distracting to some opponents.
Lassiter used to nap when seated.
I've told about "Hotel Al" before. He was in the bottom quarter of players in a local handicapped nine ball league. He was unique among his equals in realizing that he didn't play runouts as well as Earl. He knew there was no percentage in his making the 1, 2 or 3. He would try to ride the nine (smash a ball towards the nine hoping for luck) on most of his shots. When/if he played to pocket a low ball, it would be to maybe get position on a smash-and-pray shot.