I like mine oriented “broadside” vs. “straight ahead”. Just like that look better and it’s the way a knight appears on chess diagrams.
I tend to find most players like the “straight ahead” orientation.
Your preference, if any?
Diagonally, “aimed” at the center of the board.
I like mine oriented forward and my opponents’ off the board to my right.
Both inward. QN toward the h-file, KN toward the a-file. Retain these orientations no matter how often or how far they move. That way, even well into the endgame, if you have only one N left, you can still tell whether it was the QN or KN. Or if you still have both, you can still tell which was which.
Bill Smythe
As a child I always placed the knights facing forward. I suppose that is because it was the way my father set up the board. When I started competing, I thought it strange that others would place the knights sideways, until somebody pointed out that is how the knights look in diagrams.
Now I usually orient the knights so that they are staring at the opponent’s king. This knights can be intimidating.
No preference here. Just plop 'em on the board, and let’s play.
Facing forward. They hide very nicely behind large pieces like the Queen. If you put them facing sideways their little noses stick out. Never place them in the cowardly direction of facing backwards. No, the knights must always look forward. In addition, the small slits on the bishop face toward me, like little smiley faces. Kings are always centered with the cross clearly showing.
If someone placed the Knights facing backwards could the opponent “adjust” them? Would this be covered under annoying or distracting the opponent?
Once upon a time I was playing in a tournament where, on another board, both players adjusted all four knights on every move. One wanted them facing forward, the other sideways. All the “j’adoube” announcements got annoying to several players on nearby boards, so Bill Goichberg eventually ruled that each player could face his own knights, and only his own, however he wished.
Bill Smythe
Facing to the right, without exception.
Whose right?
Bill Smythe
I am. 
I face mine in the same direction as you but I knew someone in the DN era whose knights faced the edge of board, i.e., the KN pointed to the K-side and vice versa.
I just looked at some pictures of Anand, Carlson, Kasparov, Karpov and Fischer at the board with the Knights in each of their preferred orientation.
Anand has his Knights both facing straight forward.
Carlsen faces his sideways and facing towards the outside of the board, respectively. Another way to say it is he has the Knight on his right side of the board facing right and the Knight on the left side of the board facing left.
Kasparov looks to consistently have his both face sideways and to his left.
Karpov also has his Knights facing sideways. The majority of times they are both facing to his left, but there are times when they are both facing to his right. Nonetheless in a game he always has them facing in the same direction.
Bobby Fischer also appears to always have his Knights facing sideways. The majority of the pictures that showed, had his Knights both facing towards the center of the board. In one picture they were facing away from the center, but that could have been because they had traveled to the opposite side of the board during the game.
By “vice versa” do you mean that the KN pointed to the K-side, and the K-side pointed to the KN?
Bill Smythe
I seem to feel something tugging on my leg. 
For White, the queen’s horsie is pointed to White’s left.
I place mine facing inward and keep each knight facing the same direction throughout the game.
I don’t care how my opponent places his or hers, and if inward facing knights really bother an opponent, I turn mine forward. Some fights aren’t worth having.
Exactly the same for me. I’ve never had an opponent complain.
Orienting the knight may depend on how you pick up the pieces. If you use thumb, index, and middle finger to pick up the knight, then a knight facing sideways is easier to pick up. If you prefer to use two fingers, the index and middle finger, then having the knight face forward allows you to place a finger on each side of the piece to lift and place it.
In old videos I saw of Fischer playing or analyzing, he often used the two finger method of playing the pieces. The pieces were not just placed but dropped in the center of the square in a quick movement. Most players use variations of the three finger method, though I have seen grabbing the larger pieces with the whole hand. One player I know picks up the bishop at the very tip with three fingers gripping the ball at the top and then delicately placing the piece on the board. Which affectation a player acquires for moving the pieces likely comes from watching how the stronger players to it and then emulating the style.
I always have them looking forward when I set up a board. After that, I don’t them a second thought.
I’m left handed, so most likely they’re facing toward the right, after I move one.
I always place my knights so that they are “looking at” the opposing King. I don’t care how the opponent places his/hers, as long as they are reasonably centered on the square (pieces – any pieces – that are not centered on the square bother me more than anything else).
I find the “looks like a diagram” rationale amusing. If you really wanted the board to look like a diagram, you would have to lay all the pieces down on their sides, with the bottoms all facing toward the player with the white pieces – and then it still wouldn’t look like a diagram to the player with the black pieces. A properly set-up board is not going to look anything like a diagram, no matter which way you turn the pieces.