Guns :
Meta like
Frenzy was meta for a while
Stringer was equal to rifle
Bucky used to kill from medium distance one shot
Aries was better than rifles at one update
Agents:
Chamber
Jett
Astra(this I hate)
Raze (with 2 nades )
This video shows all the meta's and some insane highlight moments too and pro's reactions. I'd recommend you to watch it if you want a deeper understanding of that meta and how it played out in pro scenario