If you're a hotshot, you're extremely good at one particular thing. A young chess hotshot might win every game within the first few moves.
Hotshot is an informal word for an expert or a whiz. The math hotshot in your calculus class is probably the first person whose hand is raised to answer the teacher's question, and several colleges will no doubt try to recruit a high school basketball hotshot. While hotshot gained this meaning in the 1930s, it originally meant "reckless person," and briefly, in the 1920s, "fast train."