I haven't played 9 beyond the demo (screw Concrete Man's stage), but from what I've watched from speedruns people say Jewel Satellite is the best shield in the series.
MM9 is one of the more awesome games in the series, that and MM10. Though the platforming in these two are slightly more dangerous than other entries(MM9 in particular), any savvy MM player can handle it with relative ease.....assuming one doesn't attempt Hero/Superhero mode.
Just as everybody says, you won't find a better shield-type special weapon than the J. Satellite. Speaking of which, 9 had some of my favorite weapons in the series, L. Trident(my all time favorite), M. Bazooka, H. Chaser, etc. 10 had some pretty good ones, like W. Shield, W. Cutter, C. Spike and T. Blade.
Also, I mightttt hate on Commando Man's weapon because Blade Man's tricky to hit with it.
It's actually very easy to hit him with the bomb due to his movement patterns. He mostly moves left-to-right in a wall to ceiling pattern, which is when you shoot the Commando Bomb at the wall where he lands. Don't bother trying to use the bomb's gimmick to score hits on him, just shoot it straight at whichever wall he's moving to right underneath the spot where he lands. It's not a bad weapon, but as far as explosive-type special weapons go, it's got nothing on the Flash Bomb.
Only weapons I like from 10 are Triple Blade and Solar Blaze, but even those pale in comparison to Laser Trident. The former has too few uses/is only reliable at an even shorter range than Concrete Shot, while the latter isn't forgiving if you miss your shot.
Water Shield is okay, but Jewel Satellite is hard to let go of. Rebound Striker is okay. Everything else is garbage IMO, especially Thunder Wool (the cloud and Commando's rocket should do WAY more damage than the gimmicks they provide).
Honestly the DLC weapons are probably the best overall, but are from older games/have to pay for them.
I wouldn't say everything else is garbage, but that's me. Well, except Thunder Wool, that one was just plain crap. The Buster works better on targets that are weak to it, which says something.
Jewel Satellite is the best shield in the series by far. It does good damage, can walk/jump around with it, only disappears if a strong enemy hits it/screen change, and can be thrown. It breaks Concrete Man's stage, helps a lot in Plug Man/Wily 1, and can be used to farm health/ammo/money in certain stages/Endless Mode.
Why couldn't Mega Man have more badass shields like this?