iShares Core S&P 500 ETF (IVV)
SPDR S&P 500 ETF Trust (SPY)
SPDR Portfolio S&P 500 ETF (SPLG)
These ETFs are all well-established and widely traded, making them liquid and easy to buy and sell. They also have a low expense ratio, which means that they are relatively inexpensive to hold.
It's important to note that investing in the stock market always carries some level of risk, and there is no guarantee that any investment will perform well. However, by diversifying your portfolio and investing in a broad index like the S&P 500, you can potentially reduce your risk and increase your chances of long-term success.