Stockpile is a website that lets you buy gift cards that can then be redeemed for a variety of stocks. You can also redeem their gift cards for other merchant gift cards as well, if you’re not interested in stock. Right now Groupon has a deal where you can buy a $20 Stockpile gift card for $10. You can then apply promo code EXTRA20 for 20% off, which makes the final cost $8.
You can swap this for a Target Gift Card for example. which is probably the best option. You’re limited to only one $20 gift card per Groupon account, which is a very small limit, but could be worth doing for some savings or a small profit.