I'll set the bar and see if anyone can beat it. This example requires use of the PH and the DMG, and uses nonstandard point buy (0 points).
Character, male human Adp1/Ari1/Brd1/Clr1/Com11/Drd1/Exp1/Rog1/Sor1/Wiz1: CR 19; ECL 20; Medium-size Humanoid (human); HD 13d4+4d6+3d8-20; hp 44; Init -1; Spd 30 ft; AC 9 (-1 Dex); Melee unarmed strike +4 (1d3-1); SA sneak attack, turn undead; SQ animal companion, bardic knowledge, bardic music, nature sense, summon familiar; AL N; SV Fort +6, Ref +6, Will +18; Str 9, Dex 9, Con 9, Int 8, Wis 9, Cha 9.
SA–Turn Undead (Su): 2/day, Character can attempt to turn undead creatures. He can turn undead with no more than (1d20-8)/3 HD. Each attempt, he turns 2d6 total HD. Undead with 1/2 or fewer HD are destroyed instead.
SA–Sneak Attack (Ex): Character deals +1d6 damage against an opponent with a discernable anatomy who is denied a Dex bonus or is flanked.
Equipment: 7.6 tons of gold.
Edit: Added equipment (full 20th level baseline).