A Flashpaper Beretta 92fs is used in the flashback of Yuri shooting Bizu. When he fires, the gun does not kick back even a little, it remains perfectly still, indicating that it is a non-gun. Also note the location of the barrel.
S&W Model 36
Inspector Clouseau's (Steve Martin's) sidearm is a 5-shot Smith & Wesson Model 36 which for whatever reason he keeps in his bag instead of on his person
.22 Pistol
Agent 006 (Clive Owen) uses some sort of .22 caliber pistol mocked up as a "sleeping" gun to take out the gas mask bandits.
NYPD sidearm
A Walther P99 appears to be carried by the NYPD cops.
The soldiers who apprehend Clouseau at JFK Airport are armed with M16A1's with A2 handguards.
Mossberg 500 "Persuader"
A Mossberg 500 with a pistol grip is carried by a Gendarme member escorting Inspector Clouseau to the police HQ from the airport.
Glock 17
A 2nd Generation Glock 17 is used by a guard at the Presidential Palace. Oddly, when the guard approaches Clouseau and Ponton, his Glock makes the noise of a hammer cocking, this is impossible, as Glocks don't have external hammers. Furthermore, a matter of seconds later he cocks the imaginary hammer AGAIN after ordering the protagonists to prove they are backup dancers.