I love this song:
http://wiki.project1999.com/Denon%27s_Bereavement
In short:
-stun component
-mr debuff component
-4 poison counters (FOUR!)
-dot agro
stun = 400ish agro
poison counter = 300 per
dot aggro = ???
Mr debuff = ???
That ends up being at least 1600 aggro from stun/poison counters alone; spammable every 3 sec .... and it's pbaoe aggro.
http://wiki.project1999.com/Selo%27s_Assonant_Strane
Is great as well ... is aoe and does not break mez.
http://wiki.project1999.com/Largo%27s_Absonant_Binding
Is even greater if you just have one target ... snare slow ac and agi debuff.
But yeah the Denon's Bereavement takes the cake. Poison counters are nuts aggro and the song has 4 counters on demand + a stun (dot and mr debuff component is icing on the cake) on demand. For aoe and single target aggro, it's safe to say that no other class can really match a bard for raw threat generation potential.
Food for thought.
(Now if only we had riposte, slightly higher returns on stamina, and slightly higher defense skill .... ).