Ultimate Monk (3.5e Optimized Character Build)/Metamorphosis Forms
From D&D Wiki
 Variant #1: Lion's Wrath
Dire Lion, the critical changes:
Pounce (full attacks with charge)
Note that this particular choice makes Psionic Lion's Charge redundant (both figuratively and literally).
 Variant #2: Strength of the Bear
Dire Bear form:
 Variant #3: Thundering Lizard Spirit
Megaraptor (Size H)
Pounce (full attacks after charge)
Some people might find the idea of a monk transforming into a giant dinosaur a little silly (depends on the tone of your campaign, I guess -- and there's no way it's not impressive.) In game terms, the advantage is striking. Combined with +2 Expansion, the monk strikes as a Colossal creature, with Improved Natural Attack increasing the damage still more.
 Variant #4 Soul of Oak
The monk, by years of meditation and service to the Earth, acquires the ability to channel his chi order to to physically take on the characteristics of a mighty oak:
Trent (Size H)
Natural Armor: +13
Trample, double damage against objects.
 Variant #5 Dragon's Wrath
15HD Wyvern (Size G)
In their most desperate hour, the true masters can find within themselves the unstoppable fury of nature -- channeling the quintessence of power that is the soul of the dragon.
Natural armor: +15
Talon: 4d6 Bite: 6d6 Tail: 2d6 + poison
Gameplay notes: For the monk in trouble who has time for only one buff, this is an excellent choice. It provides Gargantuan size, massive strength, great AC, and decent natural attacks without psionic enhancement. With a +2 expansion, the wyvern form is 240 feet long and has a wingspan of 320 feet.
 Other Forms
Spirit of the Wolf (Legendary Wolf) (MM2, 137): An excellent unobtrusive form, good for confined spaces and covert operations. Size M, Str 25, Dex 28, Con 21.
Soul of the Colossus (Sun Giant): An all-out damage dealer with limited special abilities but a useful long-range attack (rock throwing, 120ft range increment.) Size H, Str 37, Dex 14, Con 25.
Eye of the Eagle, Wrath of the Lion (11HD Griffon): Able to take flight, good natural armor has (ex) pounce and (ex) rake. Size H, Str 26, Dex 11, Con 20.
Riddle of the Universe (Androsphinx): Fast on land or in the air, with fair stats, pounce, and rake; but this build truly comes into its own via the Assume Supernatural Ability feat, grant access to the androsphinx's fearsome roar. Size L, Str 25, Dex 10, Con 19.