Well anything pre 1964 (besides pennies and nickels) are 90% silver, so obviously those are the most desired. But many coins are collectable, not just silver one's.
I save all pennies before 83, all half dollars, all dollars, and everything else before 1965. Only ones really worth saving are the keydate coins. Everything else is for your own feel good.
Strange (and nice) to think that future detectorists won’t find any zinc pennies in the ground. Will they stop minting them? Would this make a person want to collect them now?
There is no hard fast rule about collecting coins. Do whatever you enjoy. Coin collecting is for the fun involved. COIN INVESTING is another thing altogether.
Just remember that virtually all collectible coins will most likely NOT go up in value.