The Matrix gun program is cheating, but still fun.
Commando, Boondock Saints, Hard Boiled all have armories.
Planet Terror, anyone? Want a M4/M203 in place of a leg? Aliens has the M41A pulse rifles and the smart gun, Starship Troopers has a bazzooka that shoots nukes. The Terminator miovies have some serious firepower in them, Does Star Wars count? Death Star laser, I win!! Lord of war has like 3,000 Vz58s in one scene, We Were Soldiers just has 10,000,000,000,000 guys runing around with guns, as does Black Hawk Down.