Cool thing about unusual openings is that they may surprise your opponent and make him play something stupid. And still if he doesn't... you will probably get at least even position, because it is you who know the theory behind your strange line. Plus your game is likely to be quite interesting and atypical.

So I was wondering, what's your favourite unusual opening?

Please post a diagram (sequence of moves) if you have time.

I'm not sure how unusual this is nowadays (it seems to getting more common lately...)

It may be a book move, but always gets my attention!

Er, 3...exf4 and Black is almost winning already :/

I have to agree with marvellosity, plus it can't be getting more common if it's not in game explorer ;)

Larsen´s opening.

Now I´ve never tried it, but it sure looks interesting.

What do you think of the Englund Gambit...?! It is probably not the choice of grandmasters, but may not be that bad at amateur level... :-)

I got so excited I created a tourney for it :-)

http://www.chess.com/tournament/englund-gambit

I'm a big fan of the king's gambit and the portuguese gambit.

For Chess.com, my favorite unusual opening is the Modern Benoni. You play that in Live Chess and it seems like the person will waste 30 seconds just trying to figure out what it is! :) It's just not that well-known here, because it's much more common to expect a KID or even a Gruenfeld at that stage.

Other than that, there's also the Ponziani Opening, although other lines are preferable (Lopez, Scotch, Italian) it's a good surprise now and then. There are, however, some troublesome lines for Black, so you need to know what you're doing.

I like it. I think I'm gonna try it in some blitz games.

I'll also sign up for the tournament! But I'm afraid there won't be much interest for such a "dubious" line. 

...well, I would sign up but

"sorry, your average time per move is too high for this tournament! You must have an average time per move less than 12 hours to register".

vandilizer

Ok, my turn. My definite all time favourite is O'Kelly Variation of the Sicillian. I fell in love with this line about 1 year ago and play it constantly from then. It looks like this:

I occasionally use the Traxler Gambit (Wilkes-Barre Counterattack).  It creates incredibly sharp play and is a good way to punish an obviously unprepared opponent.  However, it's not a particularly good choice for black, who will probably never equalize with accurate white play.

I'm also a big fan of the Tal gambit in the Caro-Kann.  However this line isn't particularly rare, nor is it dubious. 

Here are both lines...

That problem is fixed :-).

The Hippopotamus Opening! I have managed to defeat one of my friends who is quite skilled in chess at a lunchtime chess game for fun with this opening. Never usually seen in Master games.

The main line first:

And now the way my friend responded:

polleke - it's a great opening in bullet/blitz if your opponent doesn't know what they're doing

Monkey bum

yes, that's a cool variation too :-).

I like to play the Black Knights Tango.

It's sound, leads to interesting positions and not many white players know it. The main disadvantage is that you need to know the Tango's own theory, plus some lines from the Nimzo, some lines from the King's Indian, etc, and it's white's choice what it becomes. But I have a great score with it :-)

My favorite is the Caro-Kann. Many people waste precious time because they don't know how to react to this strange opening.