What Modern Coins Have The Biggest Investment Potential?

Coins bought for more than their face value will only be a good investment choice if:

1. The coins are a bullion investment and you luckily manage to buy low and sell high (e.g. buy at $4/oz back in the 90s and sell for $49/oz in 2011)
2. The coin/set was underappreciated and under-ordered when it was being made and demand far exceeds supply several years or decades later--this was the case on an EXTREMELY small number of special sets back in the 90s, such as the sets that included the '96-W dime or '98-S matte proof half.
3. The supply of coins is significantly depleted years later (the gov't hasn't done a mass meltdown since the 1930s, and the great coin melt of the 80s didn't affect the price of junk silver)
4. You get EXTREMELY lucky and get an error coin or previously undocumented variety

As previously stated, it's a craps shoot. The most critical part of getting the "best bang for your buck" is to (correctly) anticipate when a certain issue will peak in value, either in absolute terms or relative to inflation. Like a fine wine, most coins reach their prime roughly 1-20 years after release, rather than becoming more valuable on an infinitely proportional scale. A few examples:

1. The 1950-D nickel reached a peak of $25-35 in circulated grades back in the '60s. Today I can go on ebay and get a circulated '50-D for like $5, or a choice uncirculated specimen for $25ish.
2. The "godless dollars" (president dollar coins without the edge lettering) sold for several hundred dollars back in 2007 when the supply was unknown. Now they sell for $50-85ish on ebay.
3. Likewise with the 2009 cents. In 2009, people were selling $25 boxes for $250-350 each. Now they barely sell for double face value.

Certain modern coins are an excellent 1-10 year investment choice. I can't think of any that would be a good 50-100 year investment choice.

Don't invest in any coin.

There are a lot of moderns that will lead price increases over the next few decades. Many of these are world coins but US moderns also will lead the US market which won't have the spectacular increases that world coins from all centuries will enjoy. US moderns that must do well if thge hobby is to survive at all are circulating coins and just aboiut anything that's rare. I'd be a little leery of expecting good returns on coins that exist in a very narrow spread of grades. A PR-70 is not a safe bet at a large premium if most of the rest are PR-69.

Collectors need to do due diligence and in a hobby that means getting out there and finding out for yourself what is hard to find. Along the way you should sell some coins so you know their true value.

While moderns will lead the market, the only buyers who are certain to have the right coins are collectors. Investors tend to end up with coins that are easy to find and collectors end up with at least a few scarcities.

Proof cents if we decide to follow in the footsteps of Canada. The increase on their high quality penny values after the denomination was discontinued was more impressive than what I thought would happen. Other than that, I agree with everything that has been said previously especially with high quality low mintage coins. Depending on how far of an investment you are thinking, If the minting processes become even more precise than they already are, I would suggest error coins. They are always fun to collect anyway in my opinion.