With what weapons did the Man guarantee Raina's silence?

If this question relates to Act III, the man (Bluntschli) held a pistol to Raina's head in order to guarantee her silence.

With reference to Act-I I think it would be the fact that Bluntschli (whose identity isn't revealed yet) had Raina's dignity as a weapon. Raina's cloak, which was on the ottoman, was taken by Bluntschli. Buntschli stated the fact that if she were to send out an alarm, the soldiers pursuing him would see Raina in her not-so-presentable attire.

hope that helped. 

Hm... I think it was a GUN.