As others before me, I also use the Version 2 of Mojang's new textures, made by Jappa. I combine this with a little bit of Xisumavoid's Vanilla Tweaks, with the following changes (in Vanilla Tweaks, you can mix and match changes that you like, to sort of create your own texturepack):
- Hoppers with arrows on top, to see where they point
- Clearer redstone (less 'dusty', more of a clear line)
- The sides of sticky pistons have slime on them, to see in complicated contraptions if the pistons are sticky or not
- More realistic water (a lighter shade of blue, and more transparent)
- Better pumpkins (slightly less obtrusive when worn on your head) and shields (slightly smaller in the off-hand)
- Quieter netherportals