Depends on the mission. But since I have chest armors that allow bonus ammo for hand cannon & sniper OR scout & fusion, I'd probably go with:
Thorn and Patience & Time,
or maybe MIDA Multi-Tool and Pocket Infinity/Plan C.
Although, to be honest, it'd be nice to be able to just equip two exotics period. Or two weapons from the same class at the expense of not equipping another class. I'd totally go hand cannon/scout rifle and skip special weapons entirely for PvP.