When you reshape your mind blade, you can change it into a specific exotic weapon.
Prerequisites: Mind blade and shape mind blade class abilities.
Benefit: Choose one two-handed exotic melee weapon (such as the dire flail, dwarven urgrosh, orc double axe, or two-bladed sword). When you shape your mind blade, you can choose to take the form of that specific weapon. You gain proficiency with that specific exotic weapon form, but only when it is manifested as your mind blade. For example, if you have Psidarm (dire flail), you are considered to have the feat Exotic Weapon Proficiency (dire flail mind blade), but not Exotic Weapon Proficiency (dire flail).
Special: You can gain this feat multiple times. Each time you take the feat, it applies to a new two-handed exotic melee weapon.
Source: Complete Psionic, pages 49, 57, and 58. This feat replaces the Dire Flail Mind Blade, Dwarven Urgosh Mind Blade, Orc Double Axe Mind Blade, Two-Bladed Mind Blade feats on those pages. (“Psidarm” is pronounced like “sidearm”. Don’t judge. TSR and WotC had their little puns throughout the rulebooks; just look at spell material components some time. The feat name just after “Psidarm” below can be construed as a pun.) This arrangement also allows the use of two-handed exotic melee weapons outside those four.