Rock’s level 1 super, the hyper machine gun arm, strikes me as being one of the most useful assisting supers in the game due to it’s duration and stunning. So far a few characters have found uses for Megaman’s machine gun. I figured I’d start a topic where we can compile a list of useful Hyper Combos and Delay Hyper Comboes revolving around this attack.
Keep in mind that regular Hyper Combos take up 3 super bars instead of 2, but both characters will attack at the same time. Delayed Super Combos take up as much as they need to (depending on the attacks chosen) but characters only attack one at a time.
Some nice things to remember about the machine gun super is that it can be used to both keep the opponent in one place, or keep them at bay. If you DHC, the bullets stay on screen rather than disappearing, which keeps the opponent in block or hit long enough to make your teammate’s slow special seem not quite as slow as before.
Now I don’t have the game yet so a lot of this is just speculation or observation. I’d greatly appreciate if people who do have the game can help confirm/disconfirm this stuff with real testing.
Moves that come out when you use a HC with your partner
Ryu - Shinkuu Hadouken
Chun-Li - Kikou-Shou
Morrigan - Finishing Shower
Alex - Boomerang Raid
Batsu - Zenkai Kiaidan (big fireball)
Rock - Machine Gun Sweep
Soki - Joukaken
Roll - Turbo Roll Sweep
Saki - Positron Storm
Viewtiful Joe - Six Machine Cannon
Ken the Eagle - Kagaku Ninpou Bird Smash
Jun the Swan - Scratch Burst (the yo-yo super)
Casshern - Brutal Axe (the geyser)
Tekkaman - Daikaiten Tech Lancer (optic blast!)
Hurricane Polymer - Tenshin Polymer Drill (the car super)
Yatterman-1 - Tokkoutai Yatter One (the machine running across the screen)
Karas - Zaneijin
Doronjo - Zen Tehakokokara (big ball drop)
Hakusho Daimao - Honka Kutekini (punch super)
Ippatsuman - Ippatsu Gakuten Homerun
Keep in mind that if your partner is the one starting the DHC, they can use any level 1 super they want so long as it’s DHCable. So if Joe starts a DHC with Megaman assist, he can use either Six Cannon or Mach Speed in the combination.
Anyway, onto the list.
-RYU-
HC with Ryu is not too interesting. It gets lots of hits but due to damage scaling is a waste of 3 bars. Using DHC on the other hand can be quite fun since Megaman and Ryu can take turns blasting the opponent with shinkuu hadoukens and machine gun stream until they run out of super due to how simillar these two attacks are. Not too sure if it’s any good for damage, but it sure gets a lot of hits in. I don’t know if Ryu can use Megaman’s DHC to land his level 3 super, so that’s worth checking.
-Chun Li-
HC is the similar to Ryu’s, but not as interesting due to it’s small range. DHC isn’t too amazing either, at least from what I can see. There doesn’t seem to be much point in using it to combo into her rapid kick super. If Chun starts the HC using her rapid kicks, megaman might be able to prevent the opponent from being launched, allowing her to perhaps go for her infinate?
-Morrigan-
Morrigan’s missile super actually hits pretty hard but takes a short while to start up, making it a good HC. I don’t think she can do much else with DHC though. You can also have Morrigan start the HC with valkyrie turn, and Megaman should keep the opponent in stun long enough for her to return with her drill.
-Alex-
this is a mystery to me. 
I can’t see anything too interesting coming from this. Anyone think otherwise? Can he DHC to set up for power bomb or possibly stungun? Stungun can go different distances so he might be able to aim it.
-Batsu-
Seems similar to Ryu. Not too interesting it seems. His super fireball ends quite quickly, so if Batsu is the one to initiate the HC, he may be able to move before Megaman’s machine gun fire is over, allowing him to move in and continue the combo for meter building or added damage.
-Soki-
Everybody loves the machinegun + fully charged overhead slash super combo. It deals a lot of damage and is often more useful than his oni transformation (which is not a good idea unless you have 5 bars)
-Roll-
A Roll/Megaman HC is good for a few things. It either deals damage and heals either Roll or Rock, or keeps the opponent at bay while she heals. Besides that DHC doesn’t look that useful for either of them.
-Saki-
Megaman’s super lasts a lot longer than Saki’s, so perhaps she can blast the opponent up with her super, then use Megaman’s bullets to cover as she charges something up. she could also start the HC with her super ammo, then if the opponent blocks Megaman’s machine gun, she can blast them with her unblockable shot (needs testing)
-Viewtiful Joe-
machine gun + six cannon is not a bad combo. Six cannon hits very hard and can’t normally combo. A good exchange for Megaman’s low-damage level 3 super, although somehow I don’t think six cannon + machine gun deals more damage than Rock’s grab super, it’s certainly easier to land.
-PTX-40A
PTX and Megaman are a broken team because their HC is an unblockable 1 hit KO where they Gattai and then fire a lazor that fills the entire screen, so it’s not allowed in the game.
-Ken the Eagle-
not useful at all as far as I can tell. You can probably DHC the machine gun into his his DP+AB and get it to combo but wha’s the point in that?
-Jun the Swan-
I’m thinking she might be able to have a use for a HC, but it doesn’t seem like it’d be too special.
-Casshern-
same deal. I can’t think of anything too great that he could use the machine gun arm for.
-Tekkaman-
his beam super is usually a little slowish to start, but is really powerful. After a few hits from the machine gun it should start up. Quite a worthwhile HC I think.
-Yatterman-
Nice way to get Yatterman’s slow level 1 super to hit. As well as that, you can also DHC from machine gun into his flamethrower super.
-Polymar-
Machine gun + drill super is very cool. Megaman can move before Polymar stops drilling, and can even use another one if he has the super to spare. (though there are probably better things to do)
-Doronjo-
Quite a nice combination. The bullets keep the opponent busy while Doronjo’s attack starts up.
-Karas-
Looks fairly interesting. Machine gun bullets followed by Karas’s spinning sword super = a mess of projectiles that pretty much take the whole screen.
-Daimou-
I’m not so sure about this one. I believe Megaman’s bullets will push the opponent back out of the way of Hakushon’s punches.
-Ippatsuman-
It could be good if done at close range. He’d finish his baseball swing a lot sooner than Megaman finishes his machinegun attack, allowing him to move about and continue the combo, perhaps to build up a bit more meter and then finish with an air grab super.
-Gold Lightan-
Lightan scares Rock, so they can’t be partners. I think it’s the serious face in combination with that stupid voice. Also, Rock gets annoyed whenever Lightan announces himself at the end of a match.
…
I don’t know how useful all of this is going to be, but I’d like to see more lists and data coming up about stuff like this. Someone who owns the game, please correct any mistakes or untruths I (most likely) made.