So what is the best weapon in the game right now?

I prefer the Scorpion Pistol on those kits, such as Vanguards, because it makes a giant smoke-filled explosion which engulfs the enemy, making it hard if not impossible for the other three teammates to steal my kill from across the map with their Vanquishers.

If it has an X in its name it is not only good, but also cool; because anything with X in its name is good, right. Clearly though the Avenger X is the the best since its super effective when used in full auto; just give it a stability mod and a damage barrel.The barrel is only needed when playing solo to make up for the lack of DPS you should be getting from teammates, but even if you play with teammates you should bring it anyway since your teammates are too busy missing their headshots with their snipers.

The two best weapons that I'm aware of are Vanquisher and Hurricane. Both are awesome.

Black Widow is not bad at all, but it should have been demoted to rare and Vanquisher promoted to UR.

I started using the charger 10 alot lately. More than my equalizer. 

Fists

I don't understand why everyone loves the Equalizer OR the Hurricane. Both aren't accurate enough, but that's probably just me. Hurricane shreds in close combat and Equalizer is a great backup weapon. But it overheats too much.
The Vanquisher definitely looks like the best gun in the game, but I have yet to try it in MP, and the Valiant works just fine for me.
Talon's definitely good if you know how to use it. Falcon kicks ass when you learn to use it. That's about it.

Without a single doubt, Vanquisher is the dominating factor in MP right now, swiftly followed by the Equalizer.

Scattershot is also great for relaxed hold-out play.

Biotic punch or head butt

When I tried Vanquisher for the first time back in the early access,I was "wow,what a nice sniper rifle,Black widow is gonna kick ass".
Oh,boy.

There's a word called "sarcasm"

Did you know the black widow has actually been buffed in this game and does more damage than it did in me3? Black widow is really good but no one thinks so because the vanquisher is that much more op.