keyswap-mode
Chuck Hoffman, 2014

A simple minor mode to remap certain keys. Inspired by something I saw
on some blog a long time ago that I can't find now.

example configuration:

(require 'keyswap-mode)

(setq keyswap-pairs
      '((?! ?1) (?@ ?2) (?# ?3) (?$ ?4) (?% ?5)
        (?^ ?6) (?& ?7) (?* ?8) (?( ?9) (?) ?0)
        (?{ ?[) (?} ?])))

(global-set-key [M-f10] 'keyswap-mode)

Why? Because when you're programming, you type those punctuation
symbols way more than you type numbers. Now you don't have to press
shift all the time.

license: http://www.wtfpl.net/txt/copying/