New weapons for Counter-Strike 1.6:

Famas
history
design features

Galil
overview
history
Galil vs. Colt/AK-47

Ballistic Shield
(many different manufacturers)
Counter-Strike 1.5:

knife - sold as Colt CTCK

H&K USP .45 Tactical

Glock18 Select Fire

Desert Eagle .50AE

SIG P228

Dual Beretta 96G Elite
(large picture)

FN Five-Seven

Benelli M3 Super90

Benelli M4
(US Military XM1014)

H&K MP5-Navy

Steyr Tactical Machine Pistol
(no longer manufactured)

FN P90

Ingram MAC-10
(No longer manufactured)
M-11/9 sold by Cobray)

H&K UMP45

AK-47

Sig SG-552 Commando
large picture

Colt M4A1 Carbine

Steyr Aug

Steyr Scout

AWP
AWM
(Lapua .338 ammunition)

H&K G3/SG-1 Sniper Rifle

Sig SG-550 Sniper
(page includes SG-552)

FN M249 Para
(how to use it)

XM-84 Stun Grenade (flashbang)
(manufactured by BF Goodrich but they are too modest to mention it)

AN-M83 White Smoke Grenade
(military version manufactured by Combined Systems, Inc., Plainview, NY)

MK3A2 offensive grenade (H-E)
(or M67)