only a properly created cold storage or a trusted hardware wallet.
you can search for some hardware wallets if you are not tech savvy or don't want to bother learning how tos and if you are willing to pay. things such as Trezor or Ledger nano would work.
or you can learn more about cold storage and do it yourself easily. like creating a paper wallet with tools such as
https://github.com/pointbiz/bitaddress.org or make a Trezor like cold storage on your USB disk yourself
https://en.bitcoin.it/wiki/Cold_storagePrecisely, as of now there are lot of ways to keep your bitcoin safe. Some bitcoin users use online wallet to keep their bitcoin safely and secure because they know that no one will try to stealth it. However, there are some people still use the cold storage or hardware wallet. Furthermore, I think the best way to keep your bitcoin safe is to store it in online wallet.