Don't get your hopes up on new weapons or you'll probably be dissapointed when it comes out. Trust me
I thought Valve had already confirmed a couple of new weapons. At least that's what I read somewhere.
Like someone already said, bringing back the gauss gun (jump gun) would make me happy. That gun was my favorite in hl, specially with low grav on. And there is a grenade launcher in HL2, and in HL1, its called secondary fire of the SMG. They're not timed nades, though, they explode on impact, which everyone should know.