What type of grenade is the US military using right now?

Many, many different types, each fulfilling different functions. Assuming you're referring to fragmentation grenades, the M67 is still the standard fragmentation hand grenade, the M406 High Explosive and M433 High Explosive Dual Purpose rounds are the common casualty producing rounds used in the M203, and the Mk. 19 is typically loaded with M383 or M384 High Explosive or M430 High Explosive Dual Purpose munitions.