I use Oerilis Realistic resource packs and the Realistic 3D resource pack i love the 3D one it makes books on bookshelves look fallen over and in furnaces you can see the coal inside! also on brewing stands the bottles are round and poke out! everything in that pack is AWESOME! except the weapons.... they are barbaric..
Faithful (32x32) Because I like the look of the original minecraft, and let's face it, who here doesn't like an HD picture?
JohnSmith Texture pack if your looking for medieval ex. http://www.ecocitycraft.com/forum/threads/preview-grandhaven-nation-coming-soon.121481/ I also use ToqziPack for pvp
I am using my own resource pack which is what I made for myself with textural modifications in my own resource pack.