There's some funny things that happen in D&D when you screw around with distances and scales.
For example: the bard. Many people mock bards. Those people are fools.
One of the bard's most basic abilities is Inspire Courage, which lets the bard perform to grant a bonus to attack and weapon damage rolls, as well as bonuses to defend themselves against attacks that charm or frighten them. This bonus is granted to all allies who can hear the performance, and scales with the bard's level, capping out at +4 for a 20th level bard. Not too shabby.
Except for the fact that 3e never does anything by halves, so there's a pile of things that boost Inspire Courage.
The Song of the Heart feat from the Eberron Campaign Setting boosts all of your bard effects by one.
The Inspirational Boost spell from Spell Compendium boosts Inspire Courage by one.
The Badge of Valor from the Magic Item Compendium also boosts Inspire Courage by one.
Vest of Legends from the Dungeon Master's Guide II lets you function as a bard five levels higher.
The Words of Creation feat from the Book of Exalted Deeds just *doubles* your bonus. Where that multiplier comes in is kind of uncertain, with conservative estimates just multiplying your class bonus, while others argue that it should hit everything else. It comes at the cost of 3d4 nonlethal damage per round, but if you're immune to nonlethal damage by being a warforged or something, you can jam with the angels all day.
Fire it all up and you're looking at somewhere between +11 and +14 to hit and damage on every attack, which is enough to allow your party to punch way above its weight class thanks to increased accuracy while hitting like a truck in the process. Multiattackers love you because that bonus applies to every attack they make in a round, while even single attackers can profit by dumping that attack bonus via Power Attack.
If you prefer damage over accuracy, Dragonfire Inspiration from Dragon Magic lets you replace your +11 to hit and damage with +11d6 fire damage per hit, letting each attack hit with the force of a fireball. If you've got the right feats, you can add sonic damage instead, and Spell Compendium gives the creaking cacophony spell to make all enemies in range take +50% sonic damage. There's nothing stopping you from doing both either if you want attack and damage, using either two bards or a bard and a harmonizing weapon (Magic Item Compendium).
But why stop there? The bonus applies to you and any allies who can hear you sing. There's the alphorn that turns your audience into any ally within 1d10 miles, but even if that doesn't fly with your DM, there's the resounding voice spell in Heroes of Battle that lets you be heard for 100 feet per caster level. Have your cleric buddy cast a properly metamagiced version and you can basically sing for miles all day. Fortunately, even if your allies and enemies are out of sight but within earshot, there's no risk of your enemies getting hopped up on your sweet jams.
+11 to hit and damage kicks the balance around in a party of adventurers, but it completely rocks the boat when you start throwing it on a pile of weak creatures such as peasants. A proper inspiration will let someone's grandma one-punch an orc warrior- throw it on something actually dangerous and you will see results.
In one corner, we have the Mongol Horde, bent on pillaging the city.
In the other? Two bards, and every housecat they villagers could find.
Confident of their victory, the horde charges, only for the bards to begin to rock out.
And a thousand cats burst into flames, descending onto the horde in a crowd of feline fury, slaying horse and rider with a single blow each.
Bards are a ridiculous large-scale force multiplier. Fear them.