Dangerous situations can arise at the most unexpected moments. Whether you're out late at night or walking unfamiliar streets, a small personal safety tool can go a long way toward peace of mind when you might otherwise feel vulnerable. These 10 self-defense tools costing less than $20 are easily concealed or disguised and highly rated in online reviews. Of course, before buying anything that could be considered a weapon, make sure to research local and state laws to make sure it's legal where you live. And when traveling, remember to check TSA requirements to avoid confiscation.