You own a store, but you can only sell your username. What do you sell?

[nuclearblues]

two options:
a horrible weapon, the proliferation of which have led to severe consequences on the political interactions of nation-states have been disastrous and unequivocally changed the very nature of human existence;

or preferably, blues music from the cold war period. absolutely wonderful music, though that may have a bit of a limited scale when it comes to trying to properly maintain a store :P