Literally Any SPG
SPG's, or Artillery, are all very similar to eachother. Makes sense, considering they're the same class and all, but I mean really similar. With Mediums you can get some as thick and slow as the Matilda, or as fast and paper-thin as the Leopard 1. With Heavies you have the Maus, or you have something like the AMX 50 B. There can be a lot of variation, but with Artillery you always end up with more or less the same thing, save for a few differences.
Artillery has always been a mixed bag – you either love it, or absolutely despise it. Unless you're in the middle, I guess, in which case you're odd. Certainly one of the most controversial aspects of World of Tanks, but even if you hate artillery (join the club) I'd recommend playing the class a few times to understand what you're up against. By playing the class a bit you can understand some of the limitations behind the class when dealing with friendly artillery, or more importantly how to limit the amount of shells coming your way.