I just added Hancock as a companion and now I can't pull any weapons regardless of what I do! I tried loading old save files, but anytime I talk to someone, the second I come out of the conversation, I once again find that I can't pull out any of my weapons. I really don't want to start over again, and - even if I do - there's no guarantee that this won't happen again. PLEASE tell me someone has figured out a way around this bug!

I figured it out! The issue is with the Reunions mission. After you kill Kellogg, you have to talk to Nick, however he walks away and you realize you can't.... but the conversation has actually started (in the game's mind anyway). In order to fix this bug, you need to travel to Diamond City and talk to Nick at his office. The key here is, when he asks if you want him to accompany you to GoodNeighbor, you must say YES. This might trigger the conversation to start over again and you'll have to listen to everything twice, but once the conversation ends, you'll be able to pull a weapon again!