What's your favorite weapon/power-up in a shmup?

[Stilghar]

Just what the subject says

[Squire Grooktook]

I don't think any weapon can match the sheer visceral pleasure of watching an enemy mech stumble and reel as you tear into it with a Cannon Gunpod in Einhander.

Others in no particular order:

Roll Shot from Dangun Feveron
Ayin's sword in Sengoku Blade
THE SUPER BALL in OutZone
GAM in Biometal
The Homing Pods in R-Type Leo
The Lightning Shot in Daioh
The Red Flame Thrower/Laser in Fire Shark/Same!Same!Same!
All The Familiars in Guwange
The Tentacles in X-Multiply
Vulcan in Axelay
Hikaru's main laser in Macross Scrambled Valkyrie

Probably more escaping my mind at the moment lol.

[Jonst]

I'm sure there are loads I could think of, but one that instantly springs to mind is, a full stock of katanas in akai katana shin mode.

[Captain]

Dead array from hellsinker. It's melee. It's ranged. It's rapid, It's charged. It's badass.

What's not to like?

[MathU]

Gotta be the Force Device.

[copy-paster]

Black hole bomb in Darius Gaiden
Options in every Gradius-es
Capture ball in G-Darius

[Kiken]

Free Range (TFV & TFVI): Laughably broken and functionally awesome.
Shield Thunder (Gunhed): Who doesn't love all those squiggly lasers?
Sabre (TFIII): Cuts through bosses like a hot knife through butter.
Wind Laser (Axelay): Not the most useful but it looks really cool.

[ATTRACTS]

Tatsujin's skull bomb and Bornnam's winged skull bombs from the Mahou Daisakusen/Garegga games.

[Squire Grooktook]

^^^Those are cool, but we musn't forget Miyamoto's bomb in Shippu onward. That shit's rad.

[TransatlanticFoe]

Truxton 2/Gekirindan's napalm shots. Nothing like leaving a curtain of explosions!

[pegboy]

Type 2 laser in Gradius V is pretty damn fun to use.

[Shepardus]

Not a single mention of

yet?

The Hadou Gun in Ibara is a lot of fun to use. You can really feel its power both for scoring and for raw damage (speaking of which, I like how it does a ton of damage but doesn't make you invincible, encouraging you to use it offensively), and I think it's a nice way to encourage people to save up full bombs over just using bomb fragments all the time.

The freezing attack in Great Fairy Wars feels great and works super well with the scoring and survival mechanics, really giving more of the feeling that you're actually "fighting" the opponent than you get in most other Touhou games. It's also one of the few uses of graze that I actually like (grazing to speed up freeze charging). The photo mechanic in Shoot the Bullet and Double Spoiler is also really clever.

Silver Sword's bomb in Garegga and Batrider and the Black Hole Bomb in Darius Gaiden both look and sound really cool, so I think they're worth a mention even if they don't do anything special with gameplay.

[mamboFoxtrot]

Seconding CCWI Break/Double Break and Einhander Cannon.

I still haven't gotten tired of the titular Katanas in Akai Katana Shin.

The hyper beam from G-Darius is amazing, especially when beam-battling and it ends up consuming half the screen.

Most of the Cards in Trouble Witches Neo!, but especially the Fireball, Lancer thing, Bubbles (don't laugh -- those things wreck shit), and Role. The laser beam that comes from that one girl's (Louise?) Murkrow-looking bloke is pretty cool, too.

The homing lighting that the black ship from R-Type Delta uses. By continuously spamming light charges you basically become Thor, God of Lightning. Also, charge shots in the R-Type series in general.

Piercing Cannon in Mars Matrix.

Cannon weapon in Under Defeat HD. The little guy goes after enemies before they even appear on screen! So dutiful!

The grab/throw shenanigans of Cotton 2. Whether I'm throwing elemental seals or just picking enemies up raw and chucking them, I just fucking love doing it.

Borderliner, but the EX Attacks in AsteBreed. The stationary spin attack is especially good with the upgraded ship, as it does a weird delayed second hit with a larger AOE.

[Immryr]

I really like the balance between the three weapons in kamui.

[juonryu2nd]

Spread gun in SUGURI and BEAM RIFLE (H) in Sora. The dash attack at 300% feels so good.
Lightning Katana in Kamui. Though as the poster above mentioned, the other two are also satisfying to use.
That special attack you get in RefleX as Ophiuchus Zodiac.
MarisaC's flamethrowers in MoF.
Javelin and Ultimate α in Lethal Application.

[trap15]

Vertical Mine from Gradius IV. Nothing better than throwing bombs at things.
ESP Ra.De's splatter shot. Very visceral feeling, and a cool scoring mechanic to boot.

[Ixmucane2]

Best-of-class electric death:
Big straight vertical beams: the "SDF Main Gun" in Tyrian. (Honorable mention for the less elegant but better animated plasma phallus in the Dodonpachi series)
Guided toothpaste lasers: the charmingly systematic green one in Gunhed/Blazing Lazers. (Honorable mention for the spasms of the Raiden purple laser)
Lightning: Daioh has the most beautiful one.

[Sasupoika]

Hypers get me hard every time.

[davyK]

Powerful short range weapons can be very satisfying to use. I like the short range attack in Gunbird 2.

[OmegaFlareX]

The skyscraper-sized mech suit in Dogyuun. That shit blew my fucking mind first time I saw it.

Also same game, the orange homing fire weapon.

[Kino]

.

[Doctor Butler]

Hypers get me hard every time.

Anything that cancels bullets into gold.

[BrianC]

The power up that makes you invincible and plays stolen Flash Gordon music in Vanguard is awesome.

[benadiz]

Xanthez bomb from Hellsinker, level 5.
Just look at all that damage...
I love it.

[Shepardus]

Xanthez bomb from Hellsinker, level 5.
Just look at all that damage...
I love it.

I think seeing that attack is what originally got me interested in Hellsinker. I'm a real sucker for big flashy laser beams. The bomb attack in Imalice is also a good example, as is the beam rifle's super attack in Suguri.

Also, I've been playing Astebreed lately and the Wild EX attack (full lock-on + EX attack button) is really satisfying to use. The other EX attacks are too, especially when you've got a x16 multiplier and you get all those big gold numbers to show up as you dash through everything.

[Skykid]

Shout out to R-Shark's level 3 helix laser. Really satisfying.

[BIL]

Under Defeat's blue missile. Palpably heavy projectile weapon; a flying brick. Smashes heavy targets to scrap, nearby zako shatter like glass. Tricky setup, big payoff.

Seconding BioMetal's GAM, a shield meant for smashing skulls. Like Einhander's inimitable mecha pulverisings, the weapon's only half of the equation. Fish needs food, fist needs face! Boomerang shields are a really cool mechanic, paired with compelling attack/guard pressure... see also Devil Hunter Yoko on MD.

[monouchi]

Maxed Exy laser in DOJ.

[LordHypnos]

Cannon weapon in Under Defeat HD. The little guy goes after enemies before they even appear on screen! So dutiful!

It's like the polar opposite of the rocket that will just go ahead and shoot past your enemy if you were a few pixels off in aiming >_<

I also agree with the Piercing Cannon from MM. The bomb in Under Defeat is pretty awesome. Big fan of the recca bomb as well. Also like most melee attacks. The traction beam in Triggerheart is pretty sweet. The fire weapon in Fire Shark. Anchor shot in Ring^-27... Probably others I'm not remembering atm.

[Magma Dragoon]

* Flying Baron's Macross Missile Massacre in Battle Garegga.
* The Scatter Bomb in Raiden II/DX.
* Hien's bomber in Sonic Wings.