The two standard choices are nichrome (NiCr 80/20) and stainless steel (often 304). Nichrome has high, stable resistance, tolerates repeated heating, and is the classic pick; stainless is cheaper and stiffer (holds tension well) but lower resistance, so it needs more current for the same heat.
Gauge matters: thinner wire (0.3–0.5 mm) gives a narrower kerf and heats fast but is fragile and bows easier; thicker (0.5–0.8 mm) is robust and stays straighter but cuts a wider slot and needs more power. For most hobby cutters, 0.4–0.5 mm nichrome is a great default. Avoid plain steel guitar string for long runs — it oxidises and sags.
Gauge matters: thinner wire (0.3–0.5 mm) gives a narrower kerf and heats fast but is fragile and bows easier; thicker (0.5–0.8 mm) is robust and stays straighter but cuts a wider slot and needs more power. For most hobby cutters, 0.4–0.5 mm nichrome is a great default. Avoid plain steel guitar string for long runs — it oxidises and sags.