A small Kunai that is about 145mm long and relatively small, with 15% infill will print in under 40 mins, and as a bonus when you print with grid support and brim in prusaslicer and you carefully remove the support can have 2 for one as the supports have a cool  minecrafty vibe if cleaned up carefully. Be careful making this for a child as this bad boy is sharp as heck and can do some damage!