Is this the only sign for chance?
No. The fist-striking-palm sign is often used to mean a coincidence or sudden impact. Another common sign for "chance" (meaning an opportunity) uses two 'C' hands flipping downward.
Can this sign mean other words?
Yes! Because ASL is highly conceptual, this exact sign is also used for words like "impact," "affect," "strike," or "coincidence," depending on the context of your sentence.
Does it matter which hand I use to strike?
Yes, you should always use your dominant hand to perform the striking motion, while your non-dominant hand acts as the stationary base.