The Beretta-pistols seen in the Mosque shooting scene are presumed to be of the M9 model, since both Joshua Rose/Guy (Dennis Quaid) and Peter Dominic (Stellan Skarsgard) are US Marine officers and thus having the right to carry them. A Beretta 92FS is also seen in the hands of the wounded muslim who is shot.
Heckler & Koch G3A3
Heckler & Koch G3A3s can be seen in the hands of the Foreign Legion recruits in the beginning of the movie. UN soldiers are also armed with Heckler & Koch G3A3s at the prisoner exchange and at Split.
Vektor R4
The weapon makes its first appearance at the beginning, when Guy is seen being trained to its use in the Foreign Legion. Later, he is seen using it in Bosnia.
The weapon is a modified Vektor R4. The modifications seem to include a scope along with a cheek pad and removal of the sights.
With this magazine...
Heckler & Koch MP5A2
The MP5-A2 is used in the film by the Serbian soldier Goran(Sergej Trifunovic). The weapon can be identified as a A2-model by its fixed stock.
unknown SKS rifle type
The movie takes place in Bosnia during the Yugoslavian Civil War, and thus many Yugoslavian or possibly Russian weapons can be seen in the movie. Some of the militias appear to be armed with either the Zastava M59/66 rifle (local copy of the SKS rifle), regular SKS's, or even VZ52 Rifles.
Zastava M70
The Zastava M70B1 and Zastava M70AB2 rifles can be seen very briefly used by various militias and soldiers.
Zastava M57
Grenade
A grenade is seen thrown by a young girl, killing Peter (Stellan Skarsgård)
When Peter was killed, he was manning a checkpoint that had what appered to be a MG-3 mounted on the sandbags.