1.a3

Fischer used it in game 6 and 8.  Game 6 was a draw, but game 8 was a victory.

baati is starting to sound a little ignorant.  Spassky wasn't a genius?  He was the top player in the world at one point.  Fischer and him played 7 (not including the forfeit) games before Fischer managed to beat him in game 3 of the WCC.  To say a former world champion isn't a chess genius is stupid at best.  

On top of all of this, many of the world champions, including Kasparov, also used the English Opening.

1. a3 is perfectly fine. 

It is really hard to make it a loss of move in praxis and there occur many traps where the additional "a6"-moves makes quite a big difference.

Black cannot play a reversed QGA as it just loses a pawn, the reversed open Sicilian with early a3 is also very dangerous and even in the 4-knights there is a reasoning behind adding early a3. 

And even in reversed closed Sicilian or Queen's Pawn Openings a3 usually has a meaning. 

Still, e4 and d4 and likely Nf3 and c4 might be objectively better as  they restrict black's possibilities slightly more. 

On the OP's original message, here are my thoughts, even though I'm no master:

Whenever I see a strange opeining move like 1. a3, 1. h4, etc., I usually respond with 1... Nf6.  1... Nf6 seems very flexible since Nf6 is a very common move during the opening phase.  It's like saying "Ok, let's see you actually make an opening move."  It also stops 1. e4, so if white does want an e4 opening, it'll take 2 moves.  It seems to me that if white wants to play an e4 opening but wants to avoid the sicilian, black can still force it.  This would be an extreme example of white avoiding a real pawn move.

Here is an example that is a little more realistic:

Now, let's look at something else I thought of.  You mention the French defense, but what if black doesn't go for that?

Well, there is certainly a difference between 1. h3(!?) and 1. a3.

h3 is kind of dubious as it can be a weekness in many openings, while a3 is almost never a weekness and a usefull move more often than not.

Playing Queen's Gambit reveresed is pretty dangerous. White will just capture on c5 and follow up with b4, c3 and e3, which is essentially a solid pawn for free.  2. ... c5 might even deserve a question mark.

Playing the french reversed is another point. You just have to know that in case of the exchange variation, white has to play c4 early on if he wants an edge.

If white wants to play offbeat, he can also follow up with 2. b4 against more or less any reply. The Sokolsky is playable and some black replies like 1. ... Nc6 might not be the best ways to fight it.

You could try playing 1.d3 followed by 2.d4, you are now playing black. However if black is sneaky he will play 1...d6 and 2...d5 and make you white again

With 1.a3 you just take some opportunities for good transpositions in Sicilian (after 1...e5 2.c4) or Benoni (1...d5 2.Nf3 c5 3.c4), where the a3 move wasn't actually worthless. But if Black is careful he will avoid those transpositions and you've just given the advantage away.

Think of it as a psychological gambit : trading White against Black plus a chance that the opponent gives you a tempo. But you need to know every useful transposition then.

@baati : since you consider 1.c4 inferior, I guess you also consider 1.e4 c5 inferior (since it doesn't develop a bishop) ; as well as 1...e6, 1...c6 (even worse than e6 ! losing a tempo and blocking a square for the knight !). And for White, I wonder what you have against 1.Nf3 either. Maybe you want to 'push f4 sooner or later' ?

1.a3 Nf6 (huh ?) 2.Nf3 (if you've better tell me) d5 and the Benoni does not work because 3.c4 c6 kills all the fun.

Or 1.a3 d5 2.Nf3 Bg4 followed by e6, and I can't see how a3 has achieved anything. Of course it has prevented 'White' from using more ambitious systems, but Black probably keeps a very very very tiny edge.

1.a3 g6 does not seem right, indeed...

How does playing the Reversed French make 1.a3 a loss of a tempo?

People seriously underestimate the power of the French.  Many people have no clue what they're doing against the french and usually get blown right off the board.  The french is a very good opening, and people understimating it is what makes people lose against the french.  So, yeah...

It's true, the french is really correct if you know how to play it, but if black started the French with ...a6 already played, he wouldn't have the ...Ba6 maneuver he sometimes uses (after ...b6).

I have seen 1.e4 e6 2.d4 a6 played against me once, but I doubt this has good reputation among strong players.

1.a3 g6 is a line where it's most probable that the a3 move will turn out being of very little, if any, value. However, this is not critical- in most cases white can play black just as the pawn was on a2.

Black should be fine in almost all cases. The only things he should avoid is going for a reverse open Sicilian, or a reverse Benoni/ Benko, where the extra a2-a3 move could prove being very useful.

Why is this topic pinned :O?

I know I was wondering what the pin means.

And pfren, many people may go for this.  If c5 is played after d5, there's no way Black can avoid a reverse Benoni/Benko.  I play the Benko so obviously I'll go for that by responding c4. 

I'll show you some variations to make it less confusing.

Black tries to avoid the Reversed Benko with 2.Nf6, but can't...

Black immediately falls into a Reversed Benko:

So Black needs to be cautious and understand that 2.Nf5 and 2.c5 is probably not a good idea as you'll get into my repertoire that way...

The thing is that most people will fall for this because the most obvious moves are c5 and Nf6.  Nc6 is good, but I'm assuming many people won't play that.  Black will need to play Nc6 or some other move to avoid the Reversed Benko.  

Nah, not that easy....

Black isn't obliged to cooperate that much. For example, after 1.a3 d5 2.Nf3 c5 3.c4, the move 3...e6 is perfectly good. Black should be equal in most of these lines, as long as he doesn't fix the central pawn structure.

Well equality is good enough...

And, some

If Black doens't take, then we still have it fine.  Just fianchetto the King Bishop, and White should be fine.

Also, is playing 1.a3 an okay idea in OTB?

I have my first OTB tournament next week...

Any suggestions as in what to eat, how to prepare so my mind functions at its best?
times they will cooperate that much.  But even if they don't, there's not much to worry about.

If Black plays e6 then...

At our level, most people don't play the French. I've played it tons of times, but can't think of a single time I've seen it as white.  I've seen things like this a lot, but I wouldn't call it the French Defense:

IM pfren, what would you play as white's third move in this situation?

Yeah it's not a French Defense.  It's a REVERSED French Defense.

And how on earth did this topic get pinned?

I don't like 4... dxc4.  Here's an alternate 4... that I thought up.  I wonder how sound it is: