!:0
Just the name of the previous command, with no arguments.
In history-expansion counting, the command is word zero. !:0 rescues just that, ready to take new arguments.
It's the natural partner of !$: one keeps the verb, the other the object. Repeating a long command while changing only the target costs four characters.
$ rsync -av ./campo/ estufa:/coleta/
$ !:0 -av ./viveiro/ estufa:/coleta/
rsync -av ./viveiro/ estufa:/coleta/