Lemon italian ice. Lemon sorbet will work if lemon ices aren't available. (Hell, Icees or 7-11 Slurpees will work too.)
Citron Vodka or Limon Rum
Countrytime Lemonade (with sugar); Don't mix it up, the dry mix is used as a rimmer.
Ratio: 1 Italian Ice to 1 shot (not JIGGER) of booze.
Throw it in a shaker. Shake it a bit til it's all cold and slushy...
Then serve it up in chilled martini glasses which have had the rims dipped in simple syrup and then dipped into Country Time Lemonade Mix (envision the rim salted or sugared).