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Fist of the North Star
Ai wo Torimodose, the first opening song, is quite possibly the most hotblooded song ever made ("YOU WA SHOCK!! The sky falls with love!").
Fist of the North Star The music that plays whenever Kenshiro is about to kick ass! SENTOO! (which is sometimes mistaken as Ai wo Torimodose Instrumental, which it essentially is).
The second opening, "Tough Boy" by TOM* CAT. WE ARE LIVING, LIVING IN THE NINTIES! WE STILL FIGHT, FIGHTING IN THE NINTIES!
Just about every single opening song for Fist of the North Star qualify as Rated M for Manly. Here's the second opening used for the first anime, "Silent Survivor".
And here's the remake done by the same band that did the original.
Heart of Madness, the ending song of the 1986 Fist of the North Star movie, is by far one of the most awesome songs of the series.
Of course, this doesn't mean the remakes aren't full of awesome music. Check out "The Road of Lords", a song so manly that you'll feel a beard and chest hair growing out as you hear it.
The manliness aside, part of the epicness of this comes from how it essentially saves Kenshiro Den, the latest/last of the 21st-century OAVs, from a complete Downer Ending: the post-credit scene reveals that some time later, Kenshiro would stagger into a village of ruins, asking for water...
That song was created and played by Tak Matsumoto, the guitarist of the most successful band in Japan, B'z. The guy has been considered by many to be a genius guitarist and the song certainly showed it. B'z itself would later sing the theme song to the 2007 Raoh Den movie, LONELY STARS, which is very awesome as well. Here's the live version 
The French opening needs a mention. It can't compete with YOU WA SHOCK, but it's still audible, quite upbeat, and manly as well. And this is an amazing achievement when we make a comparison with all the anime from that time who got a new, and in 99% of cases craptastic, opening.
The first ending theme, Yuria... Eien Ni. Pure epic.
Kill The Fight, the theme of Fist of The North Star 2 by Masato Shimon anyone?
Futatsu no Kyoosei, the official theme of awesomeness in Fist of the North Star.
They may not be original to the series, but Gackt's Lu:Na and Oasis, the OP and ED from Shin Hokuto no Ken, certainly qualify.
Translations of the prequel, Fist of the Blue Sky, are hard to come by, but definitely something to search for. For your critique, Bara ga Saku Bara ga Chiru.
Lightseekers, from the remakes, and used for nearly every major fight therein.
Nageki No Endless from Raoh Gaiden Ten no Haoh.
Accepted Fate that plays during the saddest parts of the series in Hokuto Musou. Very much a Tear Jerker.
The Fighting Game from Arc System Works also has some pretty good themes.