Well... if you're in America I'd be cautious about adding anything. Unfortunately, American peanut butter is already heavily seasoned with sugar and salt which makes it a game of over powering the seasonings that are already in American peanut butter. But if you crush your own peanuts with a small amount of salt, as others have said do as the Asians do. Curry powder works great, cumin and as all Asians pretty much do, add some kind of hot sauce (if you can take spicy). But sadly, if you're looking at a can of jiffy, you're gonna need a lot of curry powder to overwhelm the salt and sugar content.