"What is a holy grail item you hope to find at a flea market, toy show, or comic convention?"
My current 'holy grail' is a toy I owned and loved as a kid and sadly let go many years ago: the Shogun Warriors (or World's Greatest Monsters) Rodan!
This toy was epic. It was HUGE - it could gobble up anyone from Transformers to Star Wars characters to Masters of the Universe. NO ONE COULD STOP RODAN! At least not in my toy collection. This guy was invincible.
He's super hard to find nowadays and probably pretty expensive if you do, but I've found both Blue Snaggletooth and Wonderbread He-Man in my adult life for way cheaper than I can admit and still retain your respect, and of course there was my now legendary pursuit and re-acquisition of the mythical Rabbagator, so I am sure I'll stumble onto this guy someday, and hopefully for a good price too!
Read more from the League via this handy dandy guide by Reis of Lair of the Dork Horde.
Pics via Collectiondx.com and Plaid Stallions