Pinotage said:
If I remember to come back to this thread, I'll tell you how my one and only battle against a mind flayer in 3.5e went. We're currently tracking one down in Age of Worms (Hall of Harsh Reflections) and we've not far to go now.
We did have a brief skirmish with the same one earlier. Stunned half the party with its mind blast, but a timely maximised fireball and a stinking cloud spell from our mage managed to keep it away until it fled. Now it's time for payback. Or stunback, whichever you prefer!
Pinotage
Not to worry. This time the mind flayer's toast. Or so say I. Dunwar (my aforementioned wizar) isn't as sure.
As for best mind flayer fight, the PCs in my Eberron game had a memorable one, which involved a lot more than a mindflayer. They were fighting to rescue the party alienist, who had been captured by the mind flayer leader of a segment of an ancient city now overrun by aberrations. The PCs snuck into the place and found the now-dominated alienist about to perform a vile ceremony for the mind flayer on the top of a giant ziggurat, with scores of watching aberrations. The PCs promptly attacked.
After a few seconds of a horribly chaotic battle, made even more so by the appearance of a swarm of mini-beholders (think of a mobile antimagic field), the mind flayer latched onto the orc druid berserker, who's dedicated to fighting aberrations, just as they'd been enveloped by the beholder swarm. With none of his magic working, the berserker flew into a fury and threw himself off the top of the ziggurat, holding onto the mind flayer.
As the other PCs watched in horror, the two of them bounced and rolled down the ziggurat's sides, the mind flayer boring deeper and deeper into the druid's skull and the druid trying to batter it against the stone as they fell. Finally, the two entwined enemies hit bottom with a sickening thump.
For a moment, the orc thinks he's succeeded, but then the bloodied and beaten mind flayer stirs and digs its tentacles into his brain. The druid collapses and the illithid lurches upright, about to mind blast the PCs. But one of the adventurers has already been casting, and as it straightens, a pseudonatural bison appears on either side of it. And then smash together. Scratch one mind flayer.