A deduction/exclusion that is massively under claimed amongst US expatriates is the Foreign Housing Exclusion/deduction. The exclusion/deduction works in conjunction with the Foreign Earned Income Exclusion (FEIE) and is an allowance that includes some of your housing expenses from your gross income on your US tax return.
The allowance is deductible at different thresholds depending on where you live and how many days you have lived outside of the US.