most obscure but awesome and useful opening

The Owen Defense:

Very useful, but there's almost no book, and what book there is (Staunton recommended an early c5) is wrong.  Your target is d4!  The pawn thrust which needs to be prepared is d5, and this requires considerable support from your minor pieces.  Mobilize the bishops and strike back at the center with your full fury.  The inventor of this opening, John Owen, was only an amateur, but he used it to beat Paul Morphy, Adolf Anderssen, and Wilhelm Steinitz, the latter two in the same tournament!

Warning: it is very sharp, and you need to look out for the weakness of the b5 square.  Also, do not play b6 first!  You need to start with 1. ..e6 to make sure that 2. d4 is played.  Otherwise, white doesn't need to play 2. d4.  The Owen is a hypermodern-style counter-attack, so you need a target-rich center to bring about its full effect!

Unfortunately white is usually able to gain a comfortable edge and close the center, and harass black on the kingside.

you can play the Orangutan. Great blitz opening. 1.b4

You can get pretty interesting positions, and get an advantage on the clock, if its blitz.