If you ask me who/whom let the dogs out, I'm leaving.
who
Whoever/whomever has my car keys, please return them.
Whoever
Who/whom was it that pulled your hair?
Whom
I'll give A's to whoever/whomever earns it.
whomever
Whoever/whomever want to come to the celebration is welcome to attend.
Whoever
Who/whom left the windows open again?
Who
With who/whom are you going to the homecoming dance?
whom