The 'manifester' weapon ability. For +16000 gp, you get the weapon enhancement that grants +5 power points. Not normally a problem. Except you get 50 manifester arrows for the same price, each with +5 power points, which renew themselves each day.
Also, psicrystals gain feats, RAW. One of these can be Leadership. With Improved Psicrystal, you can get a psicrystal with a minion stronger than you. Which has a psicrystal with Improved Psicrystal as well, which then has Leadership, which repeats into stronger and stronger minions until the gameworld explodes.
Your psicrystal can also take the Mounted Combat feat, and it can ride on your hat and use you as a mount. Not horrifically broken, but it's funny.
Energy conversion + Chain Power + Split Psionic Ray. Use metamorphosis, shared with your psicrystal, then schism on the both of you. That's 4 actions a round spent on firing 2 Chaining rays (each), each of which is 3 points of damage per manifester level. At ML 20, that's 8 rays dealing 60 damage apiece (more, if Overchanneled). Toss in a nice energy wall to recharge. It's not broken, but it does give massive stamina. Works well with the next combo. It's about the best damage-dealing combo you can do in psionics without going for broke, though, and running out of pp in a single fight. (Note that if you have at least two targets, you can Chain between them to make multiple attacks against multiple targets overlap.)
Greater Psionic Shot + Aligned Attack (Chaotic or Evil) + greater chasuble of fell power (Chaotic or Evil; it's in the MIC) = +7d6 for the expenditure of 2 psionic foci. Added to the previous one, that's a considerable bonus, though it's a helluvalot of feats. On most powers, like crystal shard or energy ray, make sure you use Overchannel. That's an additional +3d6 for a total of +10d6 for 2 psionic foci.
Necropolitan with telepathy (see: mindbender, totemist, etc), Lifesense, Mindsight, and detect undead. The only thing that can sneak up on you, ever, is mindless constructs.
Anthropomorphic bats. +6 Wis and flight. +0 LA.
Any buffer gish-type worth his salt (see psywar) would want an elvencraft longbow (see Races of the Wild). You can use your buffing spells and powers on one weapon (weapon of energy, graft weapon, strength of my enemy, psionic keen edge, vampiric blade), and then use it for double-duty as both a ranged and melee weapon. Also does good for deep crystal and other esoteric materials. Good when added to a bow of the wintermoon, to adjust to your Strength score when using, say, strength of my enemy.
Metamorphosis shared with your psicrystal. Go 12-headed hydra, using the hammer power, also shared with your psicrystal, for +24d8 damage on a full attack. Psicrystals keep their granted abilities when shapechanged, so you get a hydra that can fly, has (effectively) true seeing, has a climb speed, has lots of natural armor, and so on.
Vigor + share pain, both shared with your psicrystal. You not only effectively double your base hit points for 1 hour/lvl, you also gain an effective +10 temp hp per power point spent on vigor. Makes that d8 hit die of the psychic warrior (and the Psionic Body feat) look pretty good, eh?
The expansion power. Just expansion. With the extra size and the extra reach (and extra reach gained with reach weapons), you gain a +4 to lots of maneuvers (trip, bull-rush, etc), and you can prevent attacks of opportunity from those same actions by out-reaching your foes. So, basically, it replicates lots of feats to a degree if you do it right (Improved Trip, Improved Overrun, Improved Bull-Rush, Improved Disarm, etc), and keeps you from having to take those icky prereq feats (Combat Expertise? Eww!). Hustle does the same for Spring Attack (and Dodge and Mobility), Ride-by Attack (and Mounted Combat), and Flyby Attack, really.
The Linked Power feat (from CPsi) allows you to manifest a power as a free action next round if you Metapsionic a power this round. While this isn't terribly b0rked by itself, it negates one of the big problems with playing a psi-gish; namely, the necessity of buff rounds. Link grip of iron with, say, a researched schism, and then get buffed as a free action every round. Also useful for manifesting powers with looooooong manifesting times (such as psionic identify and genesis). Just Link with a power with a short manifestation time, and voila.
Strength of my enemy + bow of the wintermoon + Rapid Shot or Manyshot. Get lots of attacks to buff you and debuff enemies, all as a standard action.
Expansion (Large or Huge) + Improved Trip + Combat Reflexes + glaive + spiked gauntlet + dwarf (or half giant) = cover huge area, make lots of AoOs, make almost irresistable trip attacks to stop foes in their tracks, and do Battlefield Control much better than those silly fighters. Doable by 2nd level (or 1st, if you go human), and surprisingly effective. Add in Karmic Strike and Robilar's Gambit for more fun. Not broken, but very, very useful.
Psicrystal Affinity + claws of the beast/bite of the wolf + Improved Psicrystal + Improved Psicrystal + Improved Psicrystal + Improved Psicrystal + Improved Psicrystal + etc + etc + etc. Buff your crystal buddy and watch as it wipes the floor with the competition, due to having REALLY high HD for your level. It could also be, quite possibly, smarter than you. Flaws make this one even better. You take the penalty, your psicrystal gets the goodies.
Feat leech and a willing psionic cohort that also has bestow power. A battery and a psionic feat/spellbook, all in one.
Timeless body + 10 levels in metamind + Linked Power = infinite nova. You can spend infinite power points each round so long as you keep manifesting timeless body linked to a swift-action power. Lose your swift action each round for invincibility and infinite nova capability? Whee!
Okay, so most of the psionics stuff isn't half as good as the arcane or divine, but it's still pretty nice for a relatively balanced game.
