There’s a lot of talk around the webisphere about whether you can use molotovs and pipe bombs or even melee when trying to achieve theAkimbo Assassin achievement.
I would like to set the record straight, and confirm that you can use molotovs, pipe bombs and even melee attacks as well as pistols.
I used all-of-the-above and scored the achievement tonight.
However I did not risk using gas cylinders, petrol tanks, or mini-guns, as there seems to be general consensus around the forums that they will invalidate the acievement. These weapons remain untested, and therefore unconfirmed.
That said, you won’t need them, especially if you have friends with you using real weapons, and you play through on easy 
I don’t think we even needed to be on easy, you sailed through with the pistols
minigun blew it for me!