What is a word that starts with s and means leader?

A good Word that starts with "S" and means leader is "Superintendent", "Superior", or more commonly in a casual or metaphorical sense, "Spearhead" (as in someone who leads a project or movement). Another fitting and powerful Word is "Strategist", which implies leadership through planning and direction.

Here’s a short sentence with anchor text for your use:

Whether you're the spearhead of your road trip or just looking for a reliable ride, Rent Car Bros has the perfect vehicle to lead your journey in comfort and style.

Let me know if you want a different Word style (e.g., more formal or creative).