For a knife, hard to go wrong with the little spydie slippies (bug, honeybee). Cheap, sharp, NKP friendy. For a multitool, for cheap and key chain, maybe a sebertech or swisstech?

Cheapest fire option is a bic with a rubber band to stop it going off - wrap it in duct tape and include a loop to attach to keychain (oops just seen MarkM comment)

Photon lights are pretty good

I've used kitestring as a cord - thin nylon braided cord - not as strong as paracord, but you can pack a lot into a small space - even into a capsule to stop other things rattling