Are there investments that guarantee I'll never lose money?
Yes. There is some confusion regarding guaranteed investments and what, exactly, is protected. For starters, the only guaranteed investments which exist, safe from default, come in the form of government securities: T-Bills, notes, and bonds. Investment in a government security guarantees payment of any interest due, along with the face value of the security, at maturity. The guarantee is a default guarantee, backed by the full faith, credit and tax levying power of the United States government. The guarantee does not extend to the market value of the longer term issues (notes and bonds) which can rise and fall in response to current market interest rates. To be assured of receiving face value the owner must hold the note or bond until full maturity.
Alternatively, bank deposits such as Certificates of Deposit and other interest-bearing accounts are insured by the Federal Deposit Insurance Corporation (FDIC). A bank deposit is insured against loss in the event of a bank failure. Because bank deposits are not market investments, they are not subject to the same market risk. FDIC insurance is limited depending on the type and titling of accounts. In general, each depositor is insured up to $250,000 for all singly titled accounts, another $250,000 in aggregate for jointly held deposits and $250,000 more for aggregated retirement accounts (e.g., Bank invested IRA's).
Deposit accounts are not invested assets in the same way that IRA and mutual fund assets are invested. Invested assets are subject to market risk. The FDIC insurance protects the owner should the Bank fail, but will not protect the owner in the event invested assets, such as IRA's, lose market value.
Government securities and bank guaranteed deposit accounts serve a purpose for many investors. With the exception of TIPS (Treasury Inflation Protected Securities) they do not, however, protect against inflation. Though the loss of purchasing power is rarely as sudden as a precipitous drop in financial markets, over the long term, the erosive power of inflation can have just as devastating an effect on your financial reality. Because the asset is guaranteed, comparatively little interest is earned. Where there is virtually no risk, there is also virtually no reward.