Occasionaly if I have the opportunity to play against someone who doesn't know I play ill give bad justification for all my moves, and usually play 1.a3.
Stuff like: "ok, so my rook cant move at the moment, so im gonna put my pawn here (a3) o it has somehwere to go"
"my queen cant move either, so maybe ill play c4 so it can move as well"
My favourite troll line is a reverse scandinavian gambit if I can get it: 1.a3 e5 2.d4 exd4 3.nf3 giving really bad justifications for the moves.
After every move, look your opponent in the eyes and silently mouth the word "vacuum"
Not having taken a shower for at least a week. And it's summertime. And the torunament room is small with no open windows.
Do the Lasker move: pull a Cuban cigar in front of the player OTB and smell it, play with it, threaten to lighten it up without actually doing it.
I just got back from the restaurant. The boy at the table next to my friend and me smelled of cat urine....yucky, yuck and more yuck !....I guarantee - this will work in competition ! I kept telling myself 'don't curse the cat, don't curse the cat' (or in my next life I'll come back as a mouse).
I think THE BEST WAY is to grab your opponent's brain and start squeezing it.