That's a tough one. I like Innokin for their sense of style, though I've not had particularly good luck with all their products. I like EHPro and HCigar for their wide selection of clones, and their reputation for quality work, but I've had problems with their products, too. Right now I'm kind of a fan of Beyond Vape. They make really great
juice and a few nicely designed mods like the Neptune, though they're sadly beyond my budget. Basically, there isn't any one company I'm always happy with or would buy just anything from, because they all seem to have their specialties and weaknesses. Even the one thing that comes to mind as ultimately reliable and trustworthy and the foundation for a great vape - AW Batteries - isn't even a manufacturer. It's some guy in Hong Kong who resells Panasonic cells he's tested for quality.
I guess I'd have to go with Boge. I don't use cartomizers anymore but I can't deny they make the only ones worth getting, and they did a stellar job on my Kayfun clone.