Violin Rock remix of SA's Stage 5 theme.
This helps to imagine how fast-paced this stage is; being one of the toughest non-extra stages to date. It's long, bullets fly EVERYWHERE, and the enemies can soak up a lot of damage too. Rin Kaenbyou at the end of this stage was even worse, with her now almost iconic spell card Zombie Fairy. BRAINZ...
Sounds great at Norfair.

Arrange of Keine Kamishirasawa's theme from IN.

Sound Sepher arrange of the STG4 theme from MOF.
Caution: this remix contains large quantities of win! Not recommended for the light of heart!
I would put this as one of the Menu themes myself, as it is the perfect thing to listen to while browsing around.

Remix of 02's ever famous battle theme. Probably one of the best ones at that.

This track plays when you take on one of the team leaders.
I don't know about everyone else here, but I actually think this track is even better than the grunt theme from the same games. Just kicks WAY too much ass for me to believe otherwise. The first 2-3 seconds almost scream badass even!
Works best on Spear Pillar or Pokemon Stadium (2). (Mostly Spear Pillar though.)

Boss Theme from Megaman X5.
Sounds best at Lylat Cruise, Port Town, or Frigate Orpheon.

Generally known as the theme song of Broly from DBZ, originally from the group Pantera.
STOP BROLY, YOU'LL DESTROY THE PLANET!!
Works well almost anywhere that you want to kick someone's ass at.

Dark Phoenix arrange of Hina Kagiyama's theme from MOF.
Hina is most well-known for one of two things: absorbing bad fortune, and spinning. With the former, staying around her for too long will lead to accidents and other things happening despite her good intentions. With the latter, only 3 words can be said: SPIN HINA, SPIN!
Sounds best on Port Town... possibly Halberd too depending on the texture.

Remix found in the fangame Concealed the Conclusion of Yukari Yakumo's theme.
Odd... this is arguably my favorite version of this song. I could stand hearing this while playing Danmaku sometime... ;<
Works best on the Halberd and Spear Pillar.

BGM playing in the penultimate battle with Bowser. (When he's invincible.)
I was shocked to see that this song wasn't on the Vault yet. =w=;

Boss theme of the true final boss, Kaguya Houraisan.

Koishi's theme from SA.
Sorry... I forgot to put the DL link when I uploaded this a few minutes ago. D: Here it is.
Works best on Luigi's Mansion or some Spear Pillar textures.

Edit: Thanks goes out to KingGanondorf for pointing out a really bad typo on my part. ._.;
Arrange of Aya Shameimaru's boss theme in MOF.
The intro is so powerful. O.o It's hard to dislike this song, because of the intro instantly hooking you. xD Ah... Aya. Your theme songs are all pretty catchy. D:

Dark PHOENiX arrange of Parsee's theme from SA.
Love that guitar!! 83
Anyway... works best on Gallade64's Destination of Blazing Fires texture, Final Destination in general, or Port Town.

Remix of the Lavender/Shion Town BGM from Kanto Symphony.
...
...
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Booo!

Jazz arrange of Mystia's theme from IN, by someone known as T. Harry.
It's odd how they changed a somewhat serious-sounding song into something so relaxing and upbeat. I love this arrange. X3
Works best on New Pork, one of the Fourside stages, or Onett.

Remix of Shikieiki's theme Fate of Sixty years, that is found in the fangame CtC.
Shikieiki's theme was already awesome... This version proves that. :3
Works on Skyworld or Temple.

First level theme of DXC; an arrange of Rondo of Blood's first level theme of the same name.
The strongest Belmont of all time: Richter Belmont. Needless to say, all fake vampires should not even try to mess with him. (Not going to say names, but you know who you are!)
Place this over Norfair, Bridge of Eldin, Final Destination, Battlefield... actually, this could fit in a lot of places, except the more kid-like stages and 2D ones.

Remilia Scarlet's boss theme in Embodiment of Scarlet Devil.
Sounds best at castle stages, particularly dark ones.

BGM playing in the battle against Bowser in the Twomp Volcano and the final battle against Shrowser.
Works best at dungeon and volcanic stages.

Boss theme of PCB's Extra boss, Ran Yakumo.
Interestingly, her master's theme in this game is just an arrange of this song. But later, ZUN gave Yukari her own theme; Night Falls.
Works best on Bridge of Eldin and Castle Siege. Or any oriental stage hack.

Boss theme from MMSF2.
One of my favorite boss themes of all time... perfect for fighting to! "Wave battle, ride on!"
Works best on Battlefield and Lylat Cruise.

Upload on behalf of Sumire.
It's an orchestral arrange of Riverside View; Komachi's theme from POFV.
Works best on Bridge of Eldin or Temple.

Stage 6 theme from UFO.
Really? I was amazed to see that this hadn't been uploaded yet. It's one of the best, if not the best STG6 theme in the series. Everything contributes to this being a masterpiece, even among the other great songs in the series.
Works best on Norfair, Summit, or over one of the Subspace level themes.

Sanae's theme from Hisoutensoku/UNL.
I love this theme, including it's original version as well. GUITARS ARE FOR THE AWESOME PEOPLE! Needless to say, Sanae is cool herself. :3
Works best on certain textures for Bridge of Eldin, certain textures of Luigi's Mansion, or on some Smashville textures.