I’m in an environment where whenever I ssh to a machine I have a different username than that of my main machine. For example, the username on my desktop of “Some.Desktop.User,” whereas all the Linux environments I ssh to use the username “Some.Linux.User.” I’ve typed “ssh <host>” countless times, only to be annoyed when I realize that the password I am being prompted for is for “Some.Linux.User,” which does not exist on the host. Of course I should have typed “ssh <host> -l Some.Linux.User.”
To make life a little easier, do this:
In ~/.ssh create a file named config. In that file add the following:
Host * User Some.Linux.User
Likewise, if you have a number of different accounts on different servers, you can do something like this:
Host servername.domain User Some.Linux.User.1
Not exactly a super secret tip, but a useful time saver.
MTR 
You can also use: ssh username@host ;)
This trick + SSH certificates seem like a great combo to skip the passwords altogether.
Well yes, but this gets old when you have to ssh to 10 different machines multiple times all day long.