Of course all of this really depends on how much charisma i can acquire ...
Basically the best bet is the Linnorn or the Nightmare
Linnorn Despite having only 13hd can cast like a 17th level Cleric which means Miracle everyday!
(unlike Pitfiend which can "only" cast a wish once a year)
both are Cr20
if templates are free go for:
[spoiler]Giant Squid (Animal) 26 Str, 17 Dex, +6 NA, 10 tentacle attacks, 1 bite attack, swim 80', constrict, improved grab, +8 swim
Warbeast (Animal) +3 Str, +10' move
Woodling (Animal) +7 Natural Armour, 1 Slam attack
Magebred (Animal) +4 Str, +2 Dex, +2 NA, +10' move, Improved Natural Attacks
Voidmind (Animal) +4 Str, +2 Dex, +4 NA, +4 Bluff, Escape Artist and Intimidate, Improved Grab, One Tenticle attack, +4 to grapple
Half Golem [Brass, Clay, Dragonflesh, Flesh, Iron, Stained Glass, Stone] (Animal) +56 Str, -14 Dex, +52 NA, +2 Fortitude saves, Rage when damaged, 2 keen claw attacks
Anthropamorphic (Humanoid)
Katane (Humanoid) +2 Str, +2 Dex, +4 Listen, Hide, Move Silently and Spot
Ghul (Humanoid) +2 str, +4 Dex, +2 Climb and Jump, Bite Attack
Half-Satyr (Humanoid) +2 NA, +2 Perform
Half-Nymph (Humanoid) +2 Dex
Half-Rakshasa (Humanoid) +2 Dex, +4 NA, +10' movement
Half-Janni (Humanoid) +2 Str, +2 Dex, +1 NA
Draconic (Humanoid) +2 Str, +1 NA
Feral (Monsterous Humanoid)
Half-Troll (Giant) +6 Str, +2 Dex, +4 NA, Rend
Half-Ogre (Giant) +4 Str, +2 NA
Half-Scrag (Giant) +6 Str, +2 Dex, +4 NA
Half-Minotaur (Giant) +4 Str, +2 NA, Gore attack, +2 search
Half-Fey (Fey) +2 Dex, Fly speed (x2 land, good)
Spell-warped (Aberration) +4 Str, +2 Dex, +2 NA
Half-Dragon [x30, see MM and Draconomicon] (Dragon) +240 Str, +120 NA
Winged (Dragon)
Multiheaded (+2 heads, learnean) (Dragon)
Paragon (Dragon) +15 Str, +15 Dex, max Hp +12/HD, x3 speed, +24 AC, +25 hit, +20 damage, +13 special attack DCs, +10 saves, +10 skills, +2 feats (take as weapon focus (tentacle) and multi attack)
Effigy (Construct) +4 Str, -2 Dex, Con -, Int -, Wis 11, Cha 1, +2 NA, DR 3/Adamantine
(should be legal if applied in that order! The Creature has 47 Halfs but hey RolePlay-Genetics^^
it should equal more or less:
328 Str // 52 Dex // 215 Na apart from other minor goodies like keen claws, flying, multiple heads and things like search and Preform +2
[/spoiler]