In the trendy world of cryptocurrencies, the greatest levels of hype and anticipation have often been reserved for initial coin offerings (ICOs), the crowdsourced fundraising sales used to launch new tokens, coins and services. ICOs have come to be seen as a significant risk for the everyday investor. They are both highly speculative—since few ICOs actually go on to see the tokens they launch meet with real success—and many ICOs themselves are actually fraudulent. Nonetheless, investors continue to watch the ICO space closely for the next big opportunity. Perhaps they would do well to look for those ICOs that come closest in design to the most successful ICOs. Below, we’ll explore some of the biggest ICO events in history.

1. NEO

NEO is a Chinese open-source blockchain project that has gone by several different names in its short history. One of the most common is not an official name, however, but rather a nickname: “China’s Ethereum.” NEO gained this distinction by utilizing smart contract applications, decentralized commerce and more. The company had a massive ICO thanks in no small part to support from the Chinese government, Microsoft Corp. (MSFT), and other major companies. From an initial token price of just over 3 cents to an all-time high price of roughly $180, NEO investors who timed their investments right stood to make an incredible amount of money.

2. Ethereum

Ethereum remains the second-largest digital currency by market cap today. While bitcoin is a cryptocurrency, ethereum is both a digital currency and the foundation for decentralized applications that make use of smart contracts. Ether tokens sold for $0.31 each, and the token now sits around $700, providing a return on investment of more than 200,000% for those lucky investors who bought in during the ICO.

3. Spectrecoin

The third-most successful ICO on our list is for a cryptocurrency that has not made nearly as big of a name for itself as NEO or ethereum. Spectrecoin launched in November 2016 as a “privacy-focused cryptocurrency.” One of the features of the coin is that it can be sent and received around the world with complete anonymity. Spectrecoin pushes the boundaries of what governments around the world are willing to tolerate from digital currencies, but it has not yet broken through to the mainstream. Nonetheless, an investment of $0.001 per token back in late 2016 during the ICO would be worth close to $0.60 today, marking a significant gain.

4. Stratis

Stratis is another cryptocurrency that has not yet made it big into the world of leading digital currencies. The company, based in the U.K., prides itself on having a platform that is compatible with various programming languages, allowing businesses the ability to create and design custom applications easily. Microsoft was a prominent supporter of the Stratis ICO, and that led to major success. The project raised nearly 1,000 BTC over a period of five weeks, and individuals paid just $0.01 per token, paying off with a ROI of more than 50,000%.

5. Ark

Ark is designed to be as efficient as possible. The digital currency platform allows for quick integration of other cryptocurrencies into its own blockchain. With a global focus and a commitment to decentralization, Ark seems to have been destined for success. The initial token price was $0.04 during the ICO. At its highest levels, one Ark token climbed to nearly $11, marking a return on investment of more than 35,000%.

6. NXT

In 2013, a developer known by the handle "BCNext" launched NXT. This was one of the earliest ICOs, and it was also one of the very most successful. NXT was designed as a blockchain platform catering to the financial services sector. With tokens selling for just $0.0000168, the NXT development team managed to earn about $16,800 worth of bitcoin at the time of the ICO. This money was focused toward developing the currency associated with the platform. At its peak, NXT tokens reached as high as $2.15 each, giving investors an astonishing 1,477,000% return on investment.

One notable aspect of many of the above ICOs is that the tokens themselves are not particularly well known today. ARK is currently the 64th-most-popular digital currency, while NXT is currently the 90th according to total market cap, for instance. Because the cryptocurrency boom has been largely unpredictable, with prices rising and falling dramatically and at the slightest provocation, it can be incredibly difficult to time the sale of such tokens. Perhaps even more tricky for the budding digital currency investor, though, is identifying which potential new ICOs on the horizon could yield results with the same degree of success as the projects above. For more insight, be sure to consider all of the pros and cons of any ICO before investing, and look to our guide for advice on how to select your next cryptocurrency investment.

Investing in cryptocurrencies and other Initial Coin Offerings (“ICOs”) is highly risky and speculative, and this article is not a recommendation by Investopedia or the writer to invest in cryptocurrencies or other ICOs. Since each individual's situation is unique, a qualified professional should always be consulted before making any financial decisions. Investopedia makes no representations or warranties as to the accuracy or timeliness of the information contained herein. As of the date this article was written, the author owns cryptocurrency.