In the "Play" phase of Cribbage (31's), what is the optimal leading card to play. I have always played a 4 if I had one, because it can't be fifteened and is less likely to result in a run, because an opponent is unlikely to play a 5 or a 6. It is also not as useful as 1s, 2s or 3s at the later part of the Play when it gets close to 31.
However, I fear that this tactic is becoming too predictable, and my fellow players will know that my hand lacks a 4 if I have not played it immediately as a Leading card.
What other cards are optimal leading cards.