3E for all:
A party of 5 Bards would suck if identical in all aspects, since you can't stack the same bardic musics, and many of the buff spells they get also are morale. However, if allowed to go into different prestige classes, you coul have something like: a Bard/Crusader/Warchanter with Song of the White Raven as party Fighter; Bard/Sublime Chord for arcanist; Bard/Druid/Rogue/Fochlurian Lyricist for divine magic; Bard/Seeker of the Song or Bard/Virtuoso for the "pure" Bard; etc...
A party like that would be awesome.
Worst group is 4 black robes. Oh wait, that's FF I.
Funny thing is, my friend ran a FF 1 style game out of D&D 3E, with the classes hmodified to be al spontaneous casting and generally mesh with the game's classes. Race was also restricted to like...3 choices.

I and one other played a Black Mage and a third person made a Red Mage with a heavy offensive basis (though he had access to White Magic). Rounding out our Warriors of Light was a Fighter...
Despite our lopsided focus, we actually rocked quite hard. Eventualy the DM let in a 5th person to play White Mage for healing, ut in retrospect, we could have probably gotten by on wands. The trick was our focuses were somewhat different and worked together. My BM focused on transmutations and battlefield control, often leaving enemies stuck nigh imobile ot be utterly devastated by our party's sickening ranged damage potential, like shooting fish in a barrel. We even learned the teamwork benefit to add to save DCs of area spells if allies cast them already in the past round, and because all the mages got improved familars of some sort (mine was actually an animal companion Moogle; using UA variant) that could use magic devices, there were points of heavy bombardment where we were adding +8 to each others' save DCs! And the uh...Fighter learned to use a bow well...
[sblock]In fact, the same DM recently started a new campaign using the same material for a new group. Despite having more PCs than us initially and actually being a well balanced party, they actually got TPK'd the first session. To be fair, you start at level 1, and it is quite brutal. We ran away often from fights. But still, we handily beat that first major fight, 30+
goblins coming at us from a bridge. Mainly because I had taken Precocious Apprentice to learn Web. Which the more blasty BM then set on fire...[/sblock]
Samurai from CW: A party of them stands out the worst solely because they're the worst PC class in the entire edition... An expert could make a better PC, and in turn, a party of 5 experts would also make a better party.
My nomination for worst smae-class party: All Marshals!