I will make the assumption you are talking about towed artillery in 1/35 scale. Here are some more that I have and did not see the other two gentlemen post about.
Italeri US 57mm anti-tank gun currently under release by Zvezda as the Mk-I 6 pound anti-tank gun (#3518).
Warriors makes a US 3" anti-tank gun conversion for the Italeri M101 105mm howitzer (#319).
Italeri Zis-3 (M-42) 76.2mm Soviet anti-tank gun (#302).
Italeri German PAK 40 anti-tank gun (#318).
Not a comprehensive list, just what I happen to own.