Well the only "wallet" service that can technically work "offline" is armory. It allows you to generate private keys with an offline computer and then when you are ready to spend your bitcoin you can create a TX on an "online" computer that can then be signed by the offline computer.
I think your question is misguided. You probably want to know how to store your bitcoin offline. For best security, you will want a computer that has never "touched" the internet (meaning never connected to the internet). You then will need something that can generate a private key for you, I would recommend bitaddress.org (their git hub is
https://github.com/pointbiz/bitaddress.org). If you choose to use bitaddress then you would need to transfer a copy of the site (generally via USB drive) to your offline computer. Then you create a private key (the public key will be shown as well). You save the private key to your offline computer (and you should back it up to a second USB drive as well - at the minimum). You can use the QR code for the public key to save to your online computer so you can transfer funds to your offline computer.
When you are ready to spend your offline funds you will need to repeat the above process for a 'change' address, copy the private key onto your online computer to send a TX to your hot wallet with the change going to your 2nd newly created offline address.
I know this is not 100% what you were asking but it should help you get to your ultimate goal