I have been out with Knives,(not sucessfully, decided at the last moment how unwise I was about to be ) Bows , Firearms, and even a spear! Last 3 from a tree, so no worries there.
Like anything else, placement of the wound is the Key. I have found though that I normally see Hogs when I am hunting something else and am not specifically armed for hogs. Normally what you have will suffice if the shot is placed correctly. I still prefer something bigger though!