Paper wallet
Hardware wallets
Wallet on airgapped devices (like Electrum cold storage)
~snip~
But unlike online wallets, your seed phrase and keys will remain offline, making it impossible for online attack to be able to reveal the seed phrase and keys to online attackers.
It is wrong to call hardware wallets "offline wallets", especially if we associate it with their usual use, and for that we need the Internet - whether it's outgoing transactions, installing a coin app, or firmware update. It is true that seed is generated offline on the device and that there is currently no publicly known way to remotely hack such devices - which does not mean that one day it will not become a reality.
Every time you connect your HW to a computer or smartphone that is online, there is a possibility that something bad could happen, and I don't just mean clipboard malware.