One of the first ones is Admiral Preston Cole's victory and Death(?) at The Battle of Psi Serpentis with Battle group Indie with 13 Cruisers, 23 carriers, seventy nine destroyers, 42  frigates, 5 prowlers, and 50 repair, supply and rescue ships. Cole managed to destroy a good chunk of the covenant's fleet while losing a third of his in the first go. Later unknown friendlies (Innies maybe?) led a charge from slipspace destroying the covies fleet to half its original strength(in the area of 100-150)The rebles flee quickly and coles ship splits off his  retreating battle group and taunts every covie ship and claims "From where I sit, we (humans) are the worthy inheritors". All the covies approach his ship where he fires everything he has, then dropping 12 nukes into a nearby gas giant, making a momentary sun killing himself, and the covie fleet.

the other two battle were Sigma Octanus IV
 and Harvest