Both Zach (Vincent Pastore) and Dorthy Macha (Ray Liotta) both use Taurus PT92s. Although it is also carried by various henchmen throughout the film.
Heckler & Koch MP5K
Used by Zach (Vincent Pastore) during the alley shootout. In the film the firearm used is featured with a 30-round magazine. The firearm below is the modern variant with diopter sights attached with a 15-round magazine. The MP5K is also used by various henchmen in the film.
Except for the one in the third screenshot, all of these MP5Ks lack the diopter sights, which means that they are MP5KA1s or KA5s, depending on the trigger group ("KA1" would mean that it just has a 3-position trigger group, "KA5" would mean it has the four-position trigger group).
Glock 18
Stammering hitman Sorter (Mark Strong) carries a genuine Glock 18 as his primary weapon. He uses it with a supressor in the restaurant shootout and on full auto when he protects Jake's brother and niece.
Walther PPK
Jake Green (Jason Statham) can be seen using a Walther PPK twice. He draws one on the doctor when he confirms what Zach and Avi said and holds on Dorthy Macha (Ray Liotta), debating whether or not to kill him
A Beretta 92FS is used by one of Jake's bodyguards and by Macha's head mook
Smith and Wesson Military and Police
A snub-nosed Smith & Wesson M&P appears very briefly in the hands of one of Macha's many mooks.
Makarov PM
Macha (Ray Liotta) borrows a Makarov PM from one of his bodyguards to finish off a wounded assassin sent by Lord John
SIG-Sauer P228
After the hit on Jake in the alleyway; Sorter cradles a SIG P226 and removes a supressor while in disbelief over his missing Jake three times. It is replaced by a Glock 18 after the scene. One of Macha's bodyguards also carries a SIG in the restaurant hit.
Various Unknown Shotguns
Various unknown shotguns appear throughout the film