The old Jon-E, Zippo, Peacock, disposables...
my favorite is Peacock
What's yours?
Love the Zippo hand warmers. Very affordable to purchase and maintain. No issues with smell, especially when they stay within the bag that is included with the purchase. Lastly, they stay warm for up to 12 hours. I purchased mine at WalMart; this one is odorless.
https://www.walmart.com/ip/Zippo-Hand-Warmer-12-Hours/47930733
Personally I love the zippo ones. I usually fish with my jacket unzipped and a sweatshirt with one in, so I can take the hand I'm not using to jig with and stick it in there. They get super hot without that little black sack, and it warms your hands up super fast. I have noticed they smell, but I havent noticed my hands getting smelly from them, so it has never bothered me. Best part is they burn for hours and are super cheap compared to buying disposables over and over.