"!ssh" to run the most recent ssh command without having to type out the long list of arguments I use and the host name.

It helps to put your most frequent entries in ~/.ssh/config

  Host somewhere
  HostName somewhere.example.com
  User username
  IdentityFile ~/.ssh/somewhere_key.pub

yes and do you know about proxycommand ?

let you set up hops when you don't have direct access to a server.

e.g. if you don't have direct access to serverB but have direct access to a serverA that has direct access to serverB

put this in your ~/.ssh/config file

  host serverA
  hostname serverA.domainname.com

  host serverB
  hostname serverB.domainname.com
  ProxyCommand ssh serverA "nc %h %p"

then typing ssh serverB will log you on serverB

I also use !$ all the time. It is replaced with the last argument to the previous command line