If your accent is due to your national origin (outside the U.S.) or due to a disability/medical condition, this would be illegal discrimination: the law forbids discriminating against or harassing employees due to either national origin or disability. You could contact the federal EEOC (Equal Employment Opportunity Commission) to file a complaint and may be entitled to monetary compensation.If they are making fun of a regional U.S. accent (e.g. say you have a Boston or Chicago accent, which sounds funny to Texan ears), however, there is nothing you can do: the law does not protect on the basis of regional accents.