If you want in for the fun of it. Look into an infantry or spec ops type of job. If you want in for career training, look into aviation.

In the Army you can get a bit of both by going into aviation and being placed with a spec ops unit. The A/F you can do it by being pararescue.

Or you can go the smart route and go to the Marine Corps. You can enlist in aviation and go through all of the schools. When you get to your unit you can put in a request to try out for either Recon or SEALs. If you have the PT scores and the rifle scores you will get a chance to try out. Get through the tryout and pass through the background checks and interviews you will go to school.