If you ask me to name one gun wielding meido, the character that immediately comes to my mind is Roberta from the Lovelace Family in the anime series Black Lagoon. If you are looking for that kind intense action, you might try your luck at the Shooting Meido (シューティングめいど) Café & Bar in Akihabara.
Besides the kawaii meido-san, the first thing that catches your attention would be huge range of guns, rifles and submachine guns that are mounted on the walls and place on the tables.
They even have they guns in kawaii pink (probably for the ladies) XD
That is probably one meido café you wouldn’t want to be messing around too much. Otherwise they might just pull out a real gun and start shooting like Roberta.