I don't know if this was brought up before, but personally, I'm sick of shouting "Tipping for a transfer!" in a huge crowd of people.
I think what we need is a mail system where we will be able to send packages and letters to different characters, even in the same account (for a small fee, of course, let's say dependant on the level, like saving.). This will improve not only the bond between characters in the same account, but will also solve the "User offline, message has been buffered" messages I keep missing when I have lag. Also, you won't have to wait for a dude to login to give him money you owe him or things you need to give him.
Thank you.