Everything that's transmitted. Bitcoin node doesn't use encryption to send/receive data between nodes. BIP 151 and 324 attempt to solve that, but BIP 151 has been abandoned while BIP 324 still on development for Bitcoin Core software.
I am not talking about SPV wallets but only full node wallets.
ISP would have hard time knowing whether you only relay other's transaction or your own transaction. They would have to perform massive logging or cooperate with other ISP/government in order to determine which transaction most likely belong to yours.