I usually go with cash... sometimes I use credit or a check, but cash is my favorite. You can try using another gun, but thats not really "buying" thats more "armed robbery"... a fine distinction I admit, but its there. Knifes while still in the "armed robbery" area just don't really do the job and will usually get you shot. Pointy sticks are a personal favorite becuase they usually don't believe you until you stick 'em and then its too late for them... and if they do believe you and get all "I'm gonna shoot you" you can play it off like it was a joke and just say "hey... its just a stick man... not like I was being serious or anything".