Extracted from the wbc3 wiki:
1. Splash attacks that cause a critical hit (including a deathblow) will strike "allied" units within range. I.E: If a Giant belonging to your allies attacks an enemy unit in melee near your units, then if that Giant scored a Deathblow - then your units nearby will get hit, too, taking the obscene damage amount and being stunned!!! Morale of the story - keep away from splash damage friendly units. They could turn on you at a moments notice! FIXED
2. Splash attacks that cause a critical hit don't check along the vertical plain, allowing grounded units that can't hit aerial targets to still strike them and vice verse. I.E: If a Salamander scores a critical hit against a Swordsman, nearby fliers can also be hit, despite the Salamander being tagged to only hit grounded units. FIXED
3. Critical cleaves hits all units within horizontal range that are not on the exact side as the unit who caused this. Similar to above with the Giant, but from any unit that has a slashing type attack. Further more, it doesn't check for a unit's vertical position, allowing units like Swordsmen (who can only hit grounded targets) to hit aerial targets, or allowing Eagles (who can only hit aerial targets) to hit grounded units. FIXED
4. A unit wont cause a critical cleave if the initial target wont survive the attack, despite scoring a critical hit. This means a unit with a low damage output does better against swarms of units than those with higher damage amounts. FIXED
5. When a unit suffers a critical burn, it will cancel what ever commands it had been issued with, and replace them for the random running around if there are no enemies nearby detected by the automatic-unit-AI. This itself isn't the bug, but how a side's AI handles it is, as the AI's units only ever do what the main side's AI tells it to do. So when an AI's unit suffers a critical burn - it looses its orders and just stands there mindlessly for a few seconds before the main AI re-orders the unit to do something. I'm sure you've all seen an enemy unit charging you and then a stray fire arrow hits it with a critical burn, causing the advancing enemy unit to stop dead in its tracks. FIXED
6. Critical burns don't award kills. It's painful when you're on a quest to kill an enemy Hero and have your Fire Dragon smite one, only to see the enemy Hero run off and then burn to death - awarding no kills for you nor your Dragon, leaving your quest still incomplete! FIXED
7. Stray electrical projectiles don't cause damage if they strike a unit. This one has such a large impact on the game that players keep this in mind when using units that have these projectiles. FIXED
8. Harmless animals can be assassinated for 100 gold. I don't mind them being assassinated, but to get a bounty for killing them? I doubt anyone would put a bounty on some random Seal. FIXED
9. The same splash damage attack that destroyed a building will also hit any units immediately spawned from it (such as Lair Bosses or those fallen from towers), if the unit was spawned within the splash damage range. FIXED
10. Projectiles with the "carry though" ability will always miss all targets if it tried to hit a target immediately next to it. I.E: Barbarian spears will always miss if they're engaged in melee combat. Even if the projectile is thrown and it passes through other units, it will miss them, too. A Shame since Barbarians are one of only 2 archers in the game that had a deathblow sound, yet to hear it means nothing. FIXED
11. A suicidal unit's splash damage can't hit aerial targets, despite the unit itself being tagged to do so. The unit will still chase down aerial targets and explode - but wont inflict any damage. FIXED
12. A suicidal unit's splash damage can strike a building as many times as the splash range in squares crosses a building's grid squares, allowing units like Firebombs to do obscene damage to buildings, and in some cases, destroying them outright! FIXED
13. Units with a minimum range can still hit enemy units that are within this range if they were targeted before the enemy got within this range. FIXED
14. Electric projectiles can pass through void terrain (I.E: Cavern walls). FIXED
15. Missiles shot at certain angles have trouble hitting buildings with little art work compared to the building's full image. Typically this can be seen when attacking towers just gone under construction or when attacking the undead's Cage. FIXED