M60 is the best weapon for 1taps as it's high damage gets a 1 hit kill through most hs armour. And it's great for level maps like egypt/ship where you don't have to aim up and down just across.
M4A1 is a generally great gun however, lacks the ability to spray accurately (ak is suprememe in this aspect), but i would still recommend it.
And XM8 is the superior wallbang gp gun as it's full wallbang and has a mad scope.