See title.  This is implemented in many RTS games, and would work well in this game as well.  Often I'd like to be able to see which creeps, minions, or heroes have the lowest health without having to hover my cursor directly over their silhouette, but I can't.  I ought to be able to press alt and see the health bars of all the units nearby (friend and foe alike) and then pick and choose my targets accordingly.

As a side note, I really think all units in the game could stand to have more hitpoints (Demigods included, though to a lesser degree) because as it is they die simply too quickly to allow (or require) much finesse or selective targeting.  At least in DotA you were rewarded for getting last hits on enemies to get gold.  I'm not asking for this to be implemented, but I do believe enemies shouldn't die come in waves and die in seconds.

I think the game would have more depth and skill involved if there were fewer units in play at one time and the units that were in play were a bit sturdier so you had to think a bit more in order to eliminate them efficiently.  As it is the name of the game is just slaughter enemies en masse and try not to get stuck too long and a big group if you're low on health and don't have an AoE skill handy.