The big dud with the fangs is Sabertooth, just a younger one than we saw in the first X-Men movie. Looks like he’ll be talking in this one. 
Possible spoiler, I don’t know.
Furthermore, I think it’s hinted that he killed Wolverine’s wife, which is a large part of what led him to join Weapon X.
Gambit, of course, you saw.
Another character is The Blob. It’s unclear if he plays a major part or not. Apparently he gets into a boxing match with Wolverine. This is basically a battle until one of them falls asleep or gets bored, because neither one can really hurt the other. Well, maybe, Wolverine could cut the Blob with his claws. Maybe.
I believe the girl who turned bright white for a second is the Silver Fox. In the comics, she and Wolvie were friends (lovers?) during his days in Weapon-X, but in this movie I’m not sure.
The trailer didn’t show it, but apparently Deadpool will be there. I hope they brought in the character wholesale. He’s the “merc with a mouth”, a takeoff of DCU’s Deathstroke the Terminator, but funny and hell, insane as all-get-out, and who routinely violates the Fourth Wall. He’d actually be a much nicer guy, except that he’s been emotionally violated so many times his mind is fractured like a broken mirror. He’s sort of an antihero, and he never helps out the villains… in the end, anyway.
Other character include Beak, who I know nothing about, Agent Zero, who apparently is a super-strong dude designed specifically to kill animalistic types like Wolverine and Sabertooth, and Weapon XI. The Weapons in Marvel comics are basically the msot lethal anti-mutant killinbg machines you can imagine.