A person who is on hand and ready to perform a service or respond to an emergency; An unusually alert fellow who is capable of decisive action, seizing an opportunity.
When you need help, call me and I will be your Johnny-on-the-spot" "Oooh, thank you, girl!
Brought to public attention by Bob Woodward and Carl Bernstein in the book on the fall of Richard Nixon, All The President’s Men, ratfucker was Nixon’s term for a political operative who sows chaos among opponents; an agent provocateur. It is thought to have originated among campus political rivalries at USC, and seems to have some usage in the US military.
Along with Nixon’s other ratfuckers, Roger Stone caused fights at otherwise peaceful Democratic Party protests to generate a false narrative that the Democrats were violent and dangerous.