Rarest event from two dice and a coin

Using only two throws of a fair die and one toss of a fair coin as your randomness, you want to build an event $X$ that happens with probability $p$. What is the smallest positive $p$ you can achieve?

$1/72$. The experiment has $6\cdot6\cdot2=72$ equally likely outcomes, so any event has probability $k/72$. The smallest positive value comes from a single outcome, e.g. both dice show $6$ and the coin lands heads.