Mine would be the repeating carbine, the pump-action shotgun and the bolt-action rifle combined with either a Schofield revolver and a LeMat revolver or a Mauser and a M1899 or a second Mauser. I also have tried 2 sawed-off shotguns, and it was quite funny.
I really like the repeating carbine because it has a really good combination of accuracy, damage and rate of fire. The best thing about it is the fast reload speed though. It is absolutely amazing.
The thing I like about the pump-action is mainly its sheer power and its range. Also, I love its sound.
The bolt-action has the advantage of a really good fire rate and the ability to switch the scope on and off. Also, I find the mechanic really nice where you pull the bolt and reload.
The Schofield and the LeMat deal good damage, although their fire rate isn't great. I like their accuracy, especially the one of the Schofield. They look great as well.
The Mauser is great with its rate of fire. You can literally mow down enemies as they approach you. The M1899 is very similar.
What are your favorites?