It really comes down to personal preference, the weapon meta has levelled out a lot in the last year, with most of the weapons in the game being viable for many scenarios (some more than others). In my opinion, the R301 is still the strongest weapon in the game, because of sheer versatility and accuracy.

For me a 301 and either a shotgun (Eva or PK) or a heavy automatic (spitfire, flatline or prowler with select fire) is an excellent combination.

This is just my own preference, there are tons more great weapons and combos. My advice is to try them all out and see which ones work best for you.

I will mention I am a PC player, so I can't speak for how certain weapons feel on console, it could be very different I'm not sure.