Right now I believe the NZ-41 is the absolute medium-long range king (unless they have nerfed it recently, which I doubt) so you could risk leveling it up and pray it doesn’t get nerfed so hard.

For close range I think the H4 Blixen is great TTK-wise but I’ve seen the new Marco 5 has decent TTK and insane movement speed.

That being said, some of the weapons I often use are:

SMGs: - MP-40 (VG - the “old reliable”, competitive TTK, good mobility, easy to use) - MP5 (MW - if you have that already leveled up then it has been working perfectly for me, also easy and fun to use) - Type 100 (VG - if you’re a good player it’s fantastic, nothing can compete with its TTK but it has a very small mag and you really really need to hit your shots)

ARs: - RAM-7 (MW - some say it’s hard to use, it’s really not, it just has a strange recoil pattern, it has a competitive TTK and it’s really fun to use) - Cooper Carbine (VG - an absolute laser) - STG-44 (VG - it got nerfed recently but it’s still good) - XM4 - (CW - not really a great TTK but it’s very easy to use and it’s fun to play with once in a while).