So far, only two weapons are "definitely" confirmed:
Leon's VP-70, which he can apparently dual-wield. Chris's Beretta 92FS (because that's all he ever uses anymore).
There's also an unknown assault rifle (looks like a weird G36 or Saiga to me), plus a Colt Jake uses. Ada appears to be carrying an Arctic Warfare in the new trailer, and it looks as though Leon is using the Stakeout from Re5 in all his gameplay videos.
Guns I'd either like to see or suspect will be making appearances:
Samurai Edge as more than just a Mercenaries gun.
Silver Ghost: I was disappointed Leon was going back to the VP, because I liked this one a lot more.
Blacktail/Springfield Armory XD-9: While I hated this gun in Re4, odds are Ada will have it, since, well, she always uses it, even when it's anachronistic.
Punisher/FN FiveseveN: I loved this gun, and I'd like to see more of it.
HK USP/ P-8: This is supposedly the standard sidearm of the BSAA. Odds are we'll be seeing it again.
Steyr TMP/MP9: A fun machine pistol.
MP7: Also fun.
FN P90: This gun showed up in the hands of the FBC in Revelations. It'd be nice if we saw it again in this game.
Type 56: The Chinese AK. We are in China, after all.
FAMAS/G36/TAR 21: Traveling through Europe, I suspect we'll encounter a European assault rifle at some point.
PSG-1: My favorite sniper rifle in Re5. Seeing it again would be awesome.
Dragunov SVD: This was also a fun gun to use.
SL8: The semi-auto rifle from Re4.
MGL: Great fun for its versatility.
M79: I preferred this model. I doubt we'll see it again, but we can always hope.
SPAS-12: Good old fashioned twelve gauge shotgun.
Remington M870: Because we tend to see it a lot.
Benelli Hybrid Shotgun: These have a habit of making their way into the games. It'd be nice if we could use the semi-auto ones this time around.
Well, that's what I'd like to see. What about you?