Jim carries around a pocket knife at all times. Sometimes in case of self defence, but most of the time he's just fiddling with the thing when nothing else interests him while thinking.
It's like a sharp and dangerous stress ball for him, except only used out of sheer boredom.
When he first got it, he would end up nicking his fingers when fiddling with it. Now he's able to avoid that...or ignores it, since most of the time he's too busy with other things to notice a prick of blood on his finger.
