All non-passive specials have a corresponding attribute, that determines the power level of the special. For power level 2, the corresponding attribute has to be 14 or greater, for power level 3, 21 or greater.
Power Strike increases your damage by 66%/100%/150%, depending on your Strength. Dealing more damage means your foes go down faster which in turn means, you'll get less damage from them. Pick Power Strike for your damage dealer to deal even more damage. Pick it for any Dexterity build to compensate for the lack of Strength. Or pick it for yet another build.
Regeneration depends on your Endurance and is great in different ways. It saves you money in that you can frequently use it instead of using a healing potions. It will help you in situations where a healing potion just doesn't suffice for healing away the damage you get. Regeneration is the best special to use if you want to play as a tank. Plow through your enemies without flinching a bit. You should think about if your build really needs regeneration, though. In the end, it only allows you to endure more damage and doesn't yield any tactical options. An Endurance build using Regeneration will endure MUCH damage, though!
Nobody likes the "Miss" showing up when attacking a monster. Characters that lack a good Attack Rating (AR) like it even less. Spending some points in Dexterity is a good way to increase your AR, but what about builds that neglect Dexterity totally? A great way of compensating for low Dexterity is choosing Eagle Eye as a base special. On power level 1 it already increases your AR by 250 points, which equals about the base AR you'll have with your Dexterity at 18! Plus, it has a 5% chance to do a critical hit, effectively increasing your damage by 15%. Since the power level of Eagle Eye depends on Dexterity, it is also a good choice for Dexterity builds, giving a 12% critical hit chance. Do the math yourself!
Low Movement Cost (MC) will generally give you more tactical options, because you can often move faster than your enemies. Haste decreases the MC by 33%/45%/60%, depending on your Speed. Even if your build lacks any Speed, Haste will give you a notable boost that might just be enough to turn the tide in your favor, by allowing you to reach that pestering ranged enemy just in time, or by giving you the chance to escape from certain death. Note that Haste will also effectively increase the amount of damage you deal. Having said that, one of the most impressive builds is a Speed build using Haste. Try it out!
Picking the right special for your build isn't as obvious as one might think. The specials depend on one specific attribute, but that doesn't mean that they are useless when you don't invest in that attribute. On the other hand, getting a special to higher power levels will certainly pay off. What about a Willpower build having two base specials on power level 2?