1Password for OS/X and iOS (iPhone and iPad). Backup passwords for GMail and Dropbox are printed and stored in a safe place in my home, in case two-factor authentication doesn't work (e.g. iPhone stolen).
I do the exact same, but with the added step of adding the backup passwords for Google/Dropbox to the extra text fields you can add in 1Password. (For the very rare case of "I lost my phone/ipad, am not home for the physical backup codes, but still have access to 1Password on my Macbook")
