Ditto... any of these three will kick your butt (training is tough and each have very high wash-out rates... I suspect Rangers also have high wash-out rates).
[DANGER! war story]
One afternoon I was standing beside a road at Lackland AFB TX. in 100 degree sun, talking with a Pararescue instructor (MSgt. I think)... just shooting the breeze. As Pararescue, they all wear a dark maroon beret and you can easily identify that they are Para's by that head-gear.
Up the road comes a "herd" of Para students, I'm guessing about 30 of them, in formation, all running in their maroon shorts with their towel wrapped swim fins, goggles and snorkels tucked up under their left arm (you'll never see a Para student walking anywhere... they ALWAYS run... not "jog"... they RUN, and they always have their swimming gear with them).
As the Sgt. and I chatted, he nonchalantly looked over his shoulder behind him as the formation was about to pass us and yelled "GET DOWN YOU MAGGOTS!!" and he continued his conversation with me like nothing was going on behind him.
The Para students all stopped (on a dime) and in unison, came to attention, and yelled "YES SARGENT!". Then they all dropped to the ground and started doing push-ups and counting them out; ONE-TWO-ONE, ONE-TWO-TWO, ONE-TWO-THREE, ONE-TWO-FOUR, etc. etc.
The MSgt. and I continued our conversation for at least another 5 minutes or so while the students kept pounding out push-ups... The Sgt. never batted an eye or even acknowledged what they were doing... he just kept talking.
As we finished our conversation, he turned his head slightly over his shoulder toward the students and yelled "GET THE HELL UP AND GET THE HELL OUT OF HERE!!!"... again, he never broke stride in our conversation.
The students (in unison) all stopped doing push-ups, picked up their gear, came to attention and yelled "YES SARGENT"... then they all took off again at a dead run (to where every they were headed).
The MSgt. and I said our "so-longs" and he walked away like nothing had happened that was out of the ordinary.
I was amazed. I don't know how many push-ups those guys did... probably about 75 or so, but it seemed that they would have kept doing them until the SGT. gave them permission to stop.
I was amazed... and frankly quite glad that I WASN'T a Pararescue-man or Para-student.
It was a VERY impressive display.
Them is some "bad dudes".
[/end war story]