There are a couple I like. The T2 set is one of my favorites. It is not a set, but it is the purple recoloured T2 from BC heroics. Which I use as my transmog. There is one I use on my BE paladin from one of the pvp seasons. Not sure which one it is black and I like it. Also the pvp horde set looks good. The one from getting max rank. I have not gotten other tiers fully but I am slowly working when I don’t have other things or get bored enough to try to get parts.
On a side note you can get the horde paladin pvp look from various parts from either a vendor in shattrath or blacksmithing. I think dark iron plate chest and shoulders are the look. Not sure I will have to look.