I'm flying tomorrow, from London to Japan. With my tickets there is a handy little "Airport travel and security tips" card.
Amongst other things it says:
DO NOT pack the following items in your hand luggage:
Toy/Replica guns (metal or plastic)
Kinves with blades of any length
Hypodermic needles (unless required for medical reasons)
Billiard/snooker or pool cues
I've guessing a bo, bokken or jo looks pretty much like a snooker cue to your average airport security bloke.
Don't risk it: pad 'em, pack 'em, check 'em in.