GRE is compulsory for students pursuing an engineering degree. Some schools accept students without a GMAT score. TOEFL is compulsory for all students wishing to pursue an education in the U.S. Some universities accept IELTS instead of TOEFL.
However, please keep in mind that it is very tough to get a visa without GMAT / GRE scores. We can process your application and get you an admission in some schools without test scores. However, you may not get a visa.
Besides, a GRE / GMAT score increases the choice of universities that you can apply to as only few universities accept students without a GRE or GMAT score.