"Greatest Knights" from
Wolf Fang (AC) Gorgeous sendoff for bitterly hard-fought mecha warfare. The shimmering lead guitar, the brooding organ, the soldiering martial beat... like a lot of good HS tunes, it can sound either triumphal or elegiac, depending on how your run went.
"Sasurai no Samurai no Tomurai" from
Saigo no Nindou (AC). "Wandering Samurai's Funeral," I believe? Darkly turbulent; always makes me visualise a lonely room by candlelight, and the haunted nightscape of stage 3. Since the PCE port lacks a score table, it lends an elegant foreboding to the start menu. Masahiko Ishida's IREM BGM is unfailingly first-rate.
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Argus no Senshi (AC) Lovely little harp concerto.

A real marathon action/platformer, not especially long at ~30mins, but wickedly treacherous; this is a perfect cooldown. IIRC, you need either a high enough rank, or an ALL to hear it; there's at least one other BGM in less celebratory tone, though with the same pristine tone.
"Into The H.I." (Part 1) from
Metal Black (AC) Elegiac closer from a famously eccentric post-apocalyptic OST. I'm especially fond of the subtle organ sound YACK coaxed from the hardware. The second part is IIRC reserved for ALLs; not bad, but crash and burn for the better tune.
"Name" from
Darius Gaiden (AC) Sublimely chilled riff on the
Visionnerz motif, from OGR's inimitable weirdpop masterwork. Bittersweet right down to its title, in the series' context of unending exile war.
"We Love The E.A.R.T.H." from
Cho Ren Sha 68k (X68k) Amazingly soulful reedy warble! Loser Kashiwagi never disappoints.
"Bluescape" from
Battle Garegga (AC) 90% on Namiki lifting this from somewhere else, but as always with his Garegga OST, it works too well to ever object.
"Remember The Knights Of Legend" from
Thunder Force IV (MD) Exceptionally cool and breezy TFII reprise; I love the crisp contrast of the clanking bass and those crystal-clear leads.
"Congratulation!" from
Hyper Duel (AC) Like Gradius II's Naming BGM, this is just pure feelgood. I prefer the AC's ruggeder sound over the Saturn arrangement, but both are good. Hyakutaro Tsukumo had a legendary win streak with Tecno Soft's mid/late 90s works.
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Gradius II (AC) Unfettered joy; epitomises the good cheer of Gradius II & III's shared sound image. Motoaki Furukawa
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Super Contra (AC) Unlike most of this stomping OST, it's nothing too special - until near the end, busting out a slick arpeggio, an avalanching drum roll, and a siiick bass slap breakdown :O The crunchy tone is so good; I feel like sampling that bit for ringtones/alerts etc.
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Psyvariar 2 (AC) While I'm more fond of MU/Revision's soundtracks overall, Psyvariar 2 still has some great tunes, this being an exceptionally smooth send-off.