You could probably have some sharps, etc, in your main luggage, but every time you go on board, at least on our one cruise, you went thru a metal detector, and your carry on type stuff went thru a x-ray, just like getting onto a flight. 'Cept they don't make you take your shoes off.
I never saw them take a lighter away from anyone.

If you have a blade, or bought one ashore like we did, they take it away from you and give you a receipt. You can then pick it up the last night of the cruise (apparently they don't worry about you going postal with your blade the last night).

And, on our cruise at least, all of the security people were from Napal. They just smiled when I asked if they were former gurka...