ICAP is the best option for wallets that support it. With the ICAP option on Kraken, you must include an account ID in addition to the address so that the deposit is correctly credited to your account. Please follow the instructions carefully under Deposit > ETH > ICAP.
For wallets that don't support ICAP, Hex is the only option. Please be extra careful when sending Hex transfers because Hex doesn't have checksum, which means that it's much easier to lose your funds by entering an incorrect address.