Since it has come up a few times across the forums, below is a build that will give you every skill and still keep 6th level spells (number of possible skills in parenthesis)
Wood Elf (2)
Background (2)
1 level in Ranger (5)
1 level in Knowledge Cleric (2 with expertise)
1 levels in Bard (1)
2 more levels in bard to get Lore subclass (3, and two more with expertise)
1 last level in bard to take the skilled feat (3)
You then have 6 levels to do whatever (Wisdom or Charisma casters work best)
Because you have proficiency in everything, it wont hurt much to dump your unimportant ability scores so I would aim to have a 16 in your primary ability score and split a 14/16 between Dex and Con. That leaves 10/10/8 or 12/8/8 for your other scores. If you are doing a non-charisma character, I'd put a 12 in it just so you can benefit a little more from the bard spells.
This works okay for the half-casters, too, but you need to tweak your scores a bit.
Paladin: 16 10 16 8 10 14
Ranger: 10 16 14 10 14 12
I wont personally be using this exact build, because I don't think you need to have every skill to enjoy the game. But it is here if you are interested
