The following weapons can be seen in Zombie Loan:
Ruger Super Redhawk
Shito uses a Ruger Super Redhawk as his main weapon throughout the series. Which has a 9 1/2" barrel and a fluted cylinder.
Nogi uses the pistol, it looks like a Walther PPK. Shown on episode 11.
Heckler & Koch MP5A3
Shūuji uses the Heckler & Koch MP5A3 as his main weapon . Shown in the OVA episode 2.