Perhaps the singular most famous political ad of all times ran in 1964. Lyndon Johnson ran it against Barry Goldwater by implication, as being reckless with nuclear weapons.
Here is that ad
It officially ran only once, but was replayed multiple times, starting that campaign, and ever since.
Now Hillary Clinton has her own “Daisy” ad, and as it happens, it features the now grown-up little girl from that 1964 ad. This time the target is Donald Trump, and no doubt about that is left: