A blacksmith can create a very wide variety of iron tools and some kinds of machine parts from meteoric iron or smelted iron oxides. These tools will usually have different designs than the analogous mass-manufactured tools on Earth. The blacksmithing craft requires only other small-scale crafts for its equipment and raw materials (brick-making for the furnace and smelting for the iron bar input), thus qualifies as a small-scale craft suitable for a frontier town (small and largely self-sufficient) economy.
Steel, wrought iron, and meteoric iron
If a low-carbon smelting process is used, then the blacksmith may work in wrought iron. Its low carbon content makes it tougher and more malleable, ductile and more easily welded than modern mass-produced steel. Historically blacksmiths used wrought iron to make rivets, nails, chains, water and steam pipes, nuts, bolts, handrails, and ornamental ironwork, and swords, cutlery, and other blades. Larger factories used it to make iron structures (the Eiffel Tower is made out of wrought iron) and rails.
Given Mars' proximity to the asteroid belt and the long geological life of materials on its surface compared to Earth, meteoric iron will probably be a major source of readily worked metal. Like wrought iron, its carbon content is low. Before mankind invented iron smelting, a number of cultures used meteoric iron from the rare metallic meteorites that can be found on the Earth's surface. It was used to make spear tips, axe heads, harpoons, knives, and other edged tools, and beads and other ornaments. These required no industrial infrastructure but could be made by a single craftsman. Meteoric iron will probably work well to create almost all of the artifacts which on Earth use(d) wrought iron, and most of those that use steel.
For parts, tools, and structures used and stored outdoors, for all kinds of iron or steel, the lack of oxygen in Mars' atmosphere means rust will not be a problem.
Due to the difficulty of growing trees for wood in greenhouses, the blacksmith will have to make many items that were traditionally made out of wood. The same will probably be true, at least initially, of many items that are made out of plastic. Meteoric iron will at least initially be far more readily available than wood and most plastics.
While the Martian population is small, goods made by talented Martian artists and craftsmen out of native Martian materials will probably have high curiosity and scarcity values on Earth, and thus may fetch high premiums as collectibles.