Here is a nice, solid look at combat in Mass Effect 3. It's humorous to see footage from a game that somewhat falls on the tactical side of the third-person shooter spectrum being cut to look more action-packed.
BioWare was nice enough to throw in some gamescom screenshots as well. The one with the Reaper is particularly worth seeing. I'm also fond of the guys with faces on their shoulders. They should probably get that checked out.