Grayscale Bitcoin Trust. Unfortunately, there are certain retirement account types, college savings accounts, etc where there is no way to get BTC directly so to get those funds exposed to BTC you have to use something else. GBTC is an interesting option right now because the shares trade at -42% of there actual BTC value your getting a discount. The unknown is whether or not the fund will get converted to a Spit ETF. If it does then redemptions in BTC will be possible and the share price will go back to even. Meaning immediate 42% gain.