Straight Plug with Circuit Breaker
This is one of the coolest things that I have seen in a long time. If you are fed up of buying new jacks all the time and are looking for a solution then this is the thing for you. It is by planet waves and the jack can be fixed to the cable without being soldered! now how cool is that??
I am sure you must have seen this somewhere before. It is available in two states. one is the solid body one and the other one is a hollow one which you can put on one of your fingers and use. All the people who have seen the pink floyd pulse concert would have seen david gilmour use it in the song high hopes. If you haven't had a look at it then check it out now. That way you will also get to know what kind of cool sounds it can produce!
On stage you are always worried that your guitar may fall down if you jump around too much as it may get out of the strap. Well if you have a strap lock you can kiss your worries goodbye and give a kick ass performance.
Single string capo
This is the coolest thing i know of for an acoustic guitarist. You can place the capo on any particular string on any fret and then play your stuff. So you can try out really random and awesome sounding tunings.
This is another kick ass thing to have especially if you have a habit of losing your frets due to sweat accumulation on your hands. You can place them on the mic stand or something. So that whenever you drop one you can always pick another one up. Another alternative which is rather primitive but really effective is putting double sided tape at the bottom end of your guitar and placing a couple of pics there. That way you can drop your worries on dropping your plectrums!:)