This question could be answered so many ways, and in my case, I already found a bucket lister even though I never knew it existed (my avatar). But, here goes.
For Arrowheads and associated artifacts: A Clovis or something similar.
For Civil War Relics: Either my first U.S. Plate, first eagle button, first Confederate plate, first artillery shell, or first Kentucky related artifact. A Virginia button would be nice.
For coins: ANY DAMN SILVER COIN WILL DO! FIVE YEARS OF FUDGING CLAD!
For Colonial: This will fall under coins, but a Conn. Copper, A Virginia halfpenny, KGIII, Spanish reale or cob or pistareen, and some revolutionary war regimental buttons.
For bottles: John Ryan cobalt blue squat soda, Local Portsmouth Ohio and Ashland Kentucky amber Coca Cola straight sides (ultra rare I'm told, I already have the Huntington W.Va one, but I bought that so... I cheated).
I would like to luck upon an early settler's hidden stash. I've read that a lot of early Montana settlers and business men would hide their fortunes. I recall of one that would always want to be paid in gold coin. One of his stashes was found, but it was rumored that there was more to be found.