Just examples I guess, so I have a better idea of what you mean.
The three priorities for my bloodied powers are:
(1) Making them a spectacular example of the appropriate energy type for the character (the PCs are all magic-based and have themes)
(2) Since the PC is bloodied when he/she uses it and therefore in trouble, giving the power a defensive or healing aspect in addition to the offensive
(3) If possible, have it reinforce the PC's overall role (defender, controller, etc.)
Here are a couple of examples:
Deathly Aura
Standard action
You gain 10 + INT temporary hit points. Until the end of the encounter, any enemy that starts its turn adjacent to you takes 1d6 + WIS necrotic damage.
When you are in great pain, you can suffuse your body with writhing necrotic energy. While this energy bolsters you, you can also use it to rake any nearby enemies with black necrotic tendrils.
Storm Conduit
Standard action
Attack: CHA vs. Reflex
Blast 3
Hit: 3d10 + CHA lightning damage (half damage on a miss)
Effect: Whenever an enemy hits you with a melee attack they take CHA + DEX lightning damage and you may push them one square. This effect lasts until the end of your next turn, but may be sustained with a minor action.
When you are in great pain, you can use it to fuel an enormous burst of electrical energy, transforming your body into a living vessel of crackling blue-white lightning. You eject most of this pent up power in one devastating blast. However, with sustained effort you can keep some of the energy coiling around you, so that it shocks anyone touching you or striking you in melee.
When their PCs are badly hurt, my players certainly enjoy being able to turn the tables by busting out those bad boys.