Step 1. Have a skald or enhanced song bard in your party (or 2 or more)
Step 2. Wear Vhailor's Helm and cast simulacrum
Step 3. Have the bard and simulacrum cast mislead
Step 4. Have the bard, the simulacrum and the 2 illusions sing the bard song
Step 5. Have fun with +16 to hit, damage and AC (plus the immunities and +20 magic resistance if enhanced) for the ENTIRE party.
I think this tops the off hand weapon Melfs Minute Meteors exploit
(I hope Im not reposting a known exploit. btw after discovering this Im going to play as a half-orc fighter/thief now, too tempting for my fragile willpower to play a bard)