Filling in the gaps:

MUGEN I believe

The Black Heart

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Ok, time for something that's not a shump.

Mega Man has had his fair share of games but have you ever wanted to play as someone else? Sure!

Well, here are some Mega Man based games where you don't play as Mega Man or X or Zero or any of the regular good guys!

The Hard Hat series - As the name implies, you play as the little, nigh-indestructible Metool in a role similar to Mega Man. Blow up bosses, get weapons, blow up more stuff, you get the idea. All of the games have some sort of secret and codes to make things interesting.

Star Man - Yes, this is Star Man from Mega Man 5. The premise of the game is to prove yourself in light of a new generation of robot masters, mainly the ones from Mega Man 5 GB. It's an interesting game as you have to use the mechanics of Star Man's weapon to get through the game. This one is in the style of the Game Boy.

Star Man Upgraded - Essentially the same as Star Man except upgraded to NES-like graphics and a few additional improvements.

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RX-12 - Bydo Coefficient Test Unit

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"Hello extremely! I hope you like to *play*. Some *campers* are not so good for *games*. Is it time for *playing* yet?"

Asker: How do I remove the border on a GroupBox in .NET?
Answer: Use a panel instead?
Asker: Gee, thanks @$$.

Here we go with even more shmups! At this rate, the thread may have to be renamed as "free, downloadable shmups"... Anywho, here we go!

Here we have Hydorah, a nice, comprehensive, and challenging shmup that makes tribute to all of the classics and then some. The idea is your traditional affair, blow stuff up, get powerups, blow up more stuff, etc. but it is a fun ride. After being a stage you get a new weapon which you can select at the beginning of a stage. There are several small branching paths to go through as the game progresses and adds some good playability to it.

Ok, so this next one isn't a shmup strictly speaking but I'm sure that everyone has heard about this one. Super Mario Crossover, the game that lets you play SMB using a wide variety of characters, including soon-to-be new addition Ryu Hayabusa from Ninja Gaiden. This particular link lets you download the game and play it anytime (it's in the paragraph at the bottom of the page). Go and play!

____________________
RX-12 - Bydo Coefficient Test Unit

"No, don't try and pull any fast ones. There's nothing illegal on the Internet."

"Hello extremely! I hope you like to *play*. Some *campers* are not so good for *games*. Is it time for *playing* yet?"

Asker: How do I remove the border on a GroupBox in .NET?
Answer: Use a panel instead?
Asker: Gee, thanks @$$.

Yes, that's absolutely correct! MORE SHMUPS!

All of these are by one Linley Henzell and all are made using the Allegro gaming language, which is based in C. I'm not completely sure if these will all run in Linux or Macs but definitely Windows.

Each game has its own unique style. Two of the games, Excellent Bifurcation and Garden of Coloured Lights were both entries during the Shmup-Dev contest in different categories. My personal favorite is White Butterfly, which is more traditional but still a hack of a lot of fun. Check them out!

Also, as per the good nature of the site, Linley was nice enough to leave a copy of the source code for a few of the games. =)

Oh, if you really want your head to spin, play Excellent Bifurcation. Can you multitask?

____________________
RX-12 - Bydo Coefficient Test Unit

"No, don't try and pull any fast ones. There's nothing illegal on the Internet."

"Hello extremely! I hope you like to *play*. Some *campers* are not so good for *games*. Is it time for *playing* yet?"

Asker: How do I remove the border on a GroupBox in .NET?
Answer: Use a panel instead?
Asker: Gee, thanks @$$.