Nothing with a fancy site and testimonials, especially if they don;t sell blank carts and juice or charge more than $20 for a battery
The only "name brand" hardware site I use is Vapor4Life for my KR808D-1 stuff - they do sell juice and blank cartos
My other hardware purchases mostly come from
LiteCigUSA.net - good selection, very cheap shipping
Vaporleaf.com - good prices on 510 charger cables and some other things, a bit slower but cheap shipping
some others like Cignot.com, VaporKings.com has a good selection of parts and stuff, madvapes has parts and juices and as FreedomSmokeUSA.com
Juice companies - I mostly use FreedomSMokeUSA.com, BackwoodsBrew.net, and sometimes Velvet Vapors