In the world of a Las Vegas gaming hall, there are no clocks to tell time and no one to tell you when to stop blowing your dough. Gambling is risky business at best – or maybe reckless is more like it. The bright lights of the strip blind many casino patrons to a simple, irrefutable fact: The decks and dice are always stacked against the player.

So it goes with certain investments where playing the market is anything but fun and games. Watching a roulette wheel whirl might offer fleeting excitement, but there's nothing thrilling about seeing your investment dollars spin down the drain. Penny stocks wind up worth less than Monopoly money, and repeated stabs at market timing land somewhere between futile and foolish.

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Still, that doesn't stop the adrenaline junkies from stepping up to the table with a fistful of dollars and a head full of fantasies about the Big Score. It almost always ends up badly – and you can likewise tank if you try the eight investment categories below with anything less than wisdom, patience and experience.

Foreign exchange markets. It looks so simple – then again, so does blackjack. Too many novices see it this way: Buy loads of a slumping currency in dollars, wait for it to go back up, and buy back lots more dollars. But experts say it's like DIY plumbing: Spring a big leak and you could soon flood your financial foundation. "For do-it-yourself investors, forecasting in and attempting to profit from movements in currencies can be difficult and dangerous," says Joe Jennings, senior vice president and investment director at PNC Wealth Management in Baltimore.

Bitcoin. Maybe someday, you'll be able to feed Bitcoins into slot machines. That might produce a steadier payoff than Bitcoin itself, the mysterious virtual currency without a central bank. On Dec. 14, 2013, speculators jacked the price up to a dizzying $1,150. Eighteen days later, it fell by more than half. Today Bitcoin goes for $453.

Startups. Silicon Valley daydreams can divert attention from a real-life investor's nightmare. Report after report drives home this fact: 90 percent of startups fail. The May 16 green flag for equity crowdfunding investment promises to drum up new startup excitement, but it's not going to change the batting average anytime soon. In fact, it could attract an even higher percentage of losers. "I don't foresee most top-tier startups adopting Title III equity crowdfunding as a fundraising outlet," says Chance Barnett, CEO of Crowdfunder.

[See: 13 Money Hacks to Turbocharge Your Investments .]

'Story' stocks. Some companies have a fantastic story to tell, such as Tesla Motors (ticker: TSLA ), a pioneer in the luxury electric car market. Charismatic CEO Elon Musk predicts Tesla sales will increase tenfold by 2020. Enter the Big Bad Wolf: Tesla hasn't reported a profit in any quarter since going public. The progenitors of story stocks "are companies with big ideas but very few fundamentals to back up investors' hopes," says Jim Hardison, branch manager and managing director in the private client group at Stephen in Little Rock, Arkansas.

Market timing. You know how to time a roulette wheel, right? Of course not – so why try to time a stock? Still that doesn't deter the Smartest Gamblers in the Room. "Market timing is a scam," says Robert Novy-Marx, a professor of finance at the University of Rochester's Simon Business School. "You might get it right – and someone always does, and they're happy to tell you what a genius they are. But you are just as likely to sell too early, or get back in too late, or too soon."

Media stocks. Anxiety over the mass exodus of cable customers – known anecdotally as "cutting the cord" – has media companies reeling. A and B classes of Viacom ( VIA , VIAB ), the home of MTV, Comedy Central, BET and Nickelodeon, are down more than a third since May 2015. On the newspaper side, Chicago-based Tribune Publishing Co. ( TPUB ) is off 54 percent since splitting from Tribune Co. in 2014. Many investors hope Gannett Co. ( GCI ) will double down its $15-a-share takeover bid. TPUB currently trades at $11. But so far, no dice.

Options. Options can hedge risk when you own its underlying asset, says Yale Bock, a portfolio manager on Covestor and president of YH&C, a registered investment advisor in Las Vegas. "But if you don't, you're essentially betting on the direction of your trade; if wrong, it can force you into coughing up hard-earned dough." And in many cases, "the cash you get from selling the option is minimal relative to what you can potentially make on the asset. Conversely, the cost of protecting the downside is often large."

[Read: Decoding Wall Street's Wall of Jargon .]

Penny stocks. The name conjures images of breaking open a piggy bank on the way to breaking the bank and walking away with enough coin to fill up an armored car. In reality, penny stocks are very high-risk investments, especially for those who sink a great deal of money into them. For starters, penny stocks get almost no scrutiny because the companies aren't required to file with the Securities and Exchange Commission. Assuming you can find out anything about the stock, it's likely not credible – though the hype might be incredible.

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