The Revenge Of Shinobi | Infinite Shurikin 
> At the Option Screen, change the "Shurikin" setting to double zero (00) and wait a few seconds. The setting should change into an infinity sign and you'll be good to go.

The Revenge Of Shinobi | Unlimited Lives 
> In round 4-2 on the first platform jump and shoot to reveal a 2-up across from your position. Get it, die and repeat until your heart's content.