Well, there's the Zealot trait (+3 initiative, -1 HP per level) available to Wraiths if you're willing to train troops out of an Infirmary Fortress (grants Endurance I trait for +1 HP per level to units trained here). As for why I say 'out of an Infirmary Fortress' - Zealot + Wraith Blood means you have 0 HP per level. Adding Endurance I from the Infirmary to that brings you back to +1 HP per level. Zealot + Fast gives you +5 initiative, which is a little better than Fast + Impulsive (+4 initiative), but means that you've sacrificed whichever trait you would have put into the slot taken up by Zealot. Overall, I'd say that Zealot is bad to mediocre, depending on where you're training units.
Wraiths also have the unit trait Hallowed Rite, which generates 3 mana each time a unit with that trait kills something. This is another marginal trait but can be useful to fuel early spellcasting.
The Race of Men gets the 'Potential' trait for +25% experience, which stacks both with the 10% bonus from the blood trait and the various army experience bonuses, which can let you push your trained units up to high levels quickly to stack the level bonuses, or help counteract the penalty to the army for stacking champions (though this won't do enough to make that particularly worthwhile even so). It's a reasonable to good choice for Henchmen, but probably mediocre at best for regular troops (unless you're really stacking the level bonus traits).
Mancers get the Experienced trait, which is just like the Veteran trait except it also increases unit upkeep costs. At best, this is a mediocre trait, as one extra level does less for you than most of the other traits do, and the additional upkeep costs don't make it much more appealing.
Underdog and Bully are similar to Finesse except that they work on relative level. Having Underdog and Bully on the same unit guarantees that it gets a +3 attack bonus against anything that isn't of equal level. I don't know if these stack with Finesse, but if they do then Bully + Finesse + Fast will get you +6 attack against most computer faction troops, and Underdog + Finesse + Fast will get you +6 attack against many high-end monsters.
Unit Design Traits:
- Acrobat, +1 dodge per level, 6 production
- Balance, +10 dodge, -1 initiative, 6 prodcution
- Bloodthirsty, +25% attack versus damaged enemies, 20 production
- Brute, +3 attack versus lower level enemies, 10 production
- Charge, +1 attack and +2 movement on the first turn of combat, 20 production (can be obtained for free from Watchtower Fortresses)
- Constitution, +3 health per figure in unit, 10 production
- Defender, +10 defense when defending, 4 production
- Discipline, +1 accuracy per level, +1 spell resistance per level, 8 production
- Enmity, +25% attack versus opposite alignment (Men/Mancers/Amarians/Tarth/Ironeers are Kingdom, Quendar/Trog/Wraith/Dead/Urxen/Krax/Slave are Empire), 12 production
- Fast, +2 initiative, 15 production
- Finesse, +3 attack versus lower initiative enemies, 6 production
- Fury, +1 attack, -1 health per figure, 6 production
- Ironskin, +3 defense, 14 production
- Lithe, +10 dodge, -1 health per figure, 6 production
- Muscle, +1 attack, -1 initiative, 12 production
- Precision, +10 accuracy, 8 production
- Rage, +25% attack when under 25% health, 10 production
- Reap, +1 health each time the unit damages an enemy, 10 production
- Scout, no movement penalties, +1 sight range, 4 production
- Spell Resistance, +20 spell resistance, 6 production
- Stealth, monsters less likely to attack, 8 production
- Underdog, +3 attack versus higher level enemies, 10 production
- Veteran, +1 level when trained, 18 production
- Chain Armor Proficiency, 5 production
- Plate Armor Proficiency, 10 production
- Zealot (Wraiths only), +3 initiative, -1 health per level per figure in unit, 8 production
- Hallowed Rite (Wraiths only), +3 mana per kill made by this unit, 8 production
- Experienced (Mancers only), +1 level when trained, +1 gildar per turn upkeep (unsure if this is per figure or not), 25 production
- Road Building (Mancers only), 10 production
- Potential (Race of Men only), +25% experience gain, 8 production
- Endurance I (Infirmary Fortress), +1 health per level per figure, free
- Impulsive (Strike Garrison Fortress), +2 initiative, free
- Charge (Watchtower Fortress), same as the other Charge
Out of the above, Balance and Lithe do more or less the same thing but Balance has the more severe penalty (-1 initiative from Balance, as compared to Lithe's maximum of -6 health, which basically sets its health half a level behind an equal level equal size unit; Ironeer blood or the Endurance I trait make this a third of a level, while Wraith blood makes this a full level, but regardless this is practically nothing). Fury and Muscle also do more or less the same thing, with Fury being clearly superior as it's once again up to -6 health compared to -1 initiative as well as being half the cost of Muscle. Reap and Rage are kind of useless (Reap's healing is not per figure; if you have a 1 figure unit with Reap, it will heal exactly the same amount as a 6 figure unit with reap will each time it does damage; Wraith Blood has the same issue), and Enmity is a better form of Bloodthirsty if you can guarantee that you'll only be fighting opposite-alignment foes with the unit.
Dodge-based units should probably take Balance + Lithe + Acrobat, though if you want to sacrifice any of these traits to take something else (like Fast), I'd sacrifice Balance first. More or less the only reason to take Precision or Discipline is that you're fighting a good dodge-based unit. Discipline and Spell Resistance can toughen a unit against spells, but a mid-level Mage champion, or even a high level non-Mage champion, will blow through any amount of spell resistance a trained unit can come up with so this is mostly a defense against spellcasting monsters and low-level champions. In my opinion, if you're going to take dodge traits, you should probably go all-out; lots of dodge is much more useful than just a little, and Acrobat is necessary to prevent your dodge-based defenses from being eroded by the accuracy bonus from unit levels (+1 per level, +1 more per level for Mancer Blood, +1 more per level with Discipline; Acrobat will cancel out one of these bonuses by granting +1 dodge per level). Especially with Wraith Blood, it may be tempting to sacrifice one of the +10 dodge traits, but remember that hit chances are computed as (Attacker Accuracy) - (Defender Dodge), and with Wraith Blood + both 10 dodge traits + the 10 dodge robe you can get to 50 dodge (meaning a 20% hit chance for a 70-accuracy unit, about normal for low-level trained troops); dropping down to 40 dodge from this point means that that same 70-accuracy unit hits roughly 50% more often and on average hits for more damage. The difference in the potency of dodge-based defenses gets lower when comparing smaller dodge values, e.g. a 10-dodge unit will be hit 20% more often by a 70-accuracy unit than a 20-dodge unit will, though this is still a significant difference if you're basing your defense around dodging attacks (note also that the higher dodge units will also be hit for on average less damage than the lower dodge units because each figure in a unit makes a separate attack role when determining hit damage). Also note that since units gain accuracy with levels, Acrobat is almost essential for preserving the utility of your dodge-based units against high-level opponents.
Veteran and Experienced are not, in my opinion, worth taking; the production cost is too high and you really don't gain that much from just one extra level, especially if you're training out of a Fortress that already grants a couple extra levels. Henchmen and Sions are an exception to this rule, as they gain traits like champions do and so a free level may be a good deal for them.
Scout is a useful mobility enhancement for your armies, but you'll have to sacrifice something for it. Might be worthwhile if there is a lot of rough terrain around your territory and your champions have compasses or some other way to make up for terrain penalties (e.g. mounts when you're using infantry troops). Stealth isn't worth using except on lone units.
Brute, Underdog, and Finesse all offer about the same thing with different conditions; of them, Finesse is probably the most useful as it's relatively easy for the player to ensure the initiative advantage over computer faction troops and most monsters. None of these are bad, though Underdog will lose its utility if you keep your troops alive and develop them to a high level.
Constitution and Ironskin are both good traits for blood tanks. Constitution grants 1.5 levels worth of health to an average unit, which isn't great but helps with tanking or to counteract health penalties (e.g. Wraith Blood, in which case Constitution grants 3 levels worth of health, or Lithe or Fury). Ironskin makes a unit generally harder to kill and can be especially valuable in the early stages where at best you have leather armor. Defender is good for a tank that is meant to sit still and block (possibly with counterattacks if using a sword unit; this is a case where the initiative penalties of Muscle and Balance might be less of an issue than the health penalties of Lithe and Fury, as the unit is just intended to block the enemy's melee line rather than to be a main damage dealer, and initiative is not that important in this role), but is mostly useless on a unit meant to make attacks on its turns.