2e Mind Flayers had unlimited mental blasts in the
Monstrous Compendium.
MC1:
"Combat: A mind flayer can use its four tentacles in combat. If a tentacle hits, it will reach the opponent's brain in 1-4 rounds, drawing it forth and killing the victim. The mind flayer then devours the brain. Even more deadly than this is the mind flayer's mental blast, which spreads in a cone 60 feet long, 5 feet wide at the base and 20 feet wide at its end; all within the area of effect must save versus wands at -4 or be stunned for 3-12 (d10 + 2) rounds.
The mind flayer's mental talents also allow it to use the following powers, one per round, as a 7th level mage: suggestion, charm monster/person, ESP, levitate, astral projection, and plane shift. Mind flayers have infravision. All saving throws against a mind flayer's mental powers are at -4, due to its powerful mental force."
The Complete Psionics Handbook gave alterations to the mindlfayer stat block using the psionicist point rules instead of at will default ones. I remember thinking that seemed more cumbersome to track as a DM when I saw it.