PayPal "Goods & Services" is generally the best - buyer pays a small fee 'protection' that I've never needed to test but it's better than "Friends & Family" or Venmo where you are just out the money if nothing gets shipped. Venmo didn't seem to accept my Google Voice number, and lots of places know flag numbers that are from similar services.
Facebook marketplace is great for selling locally when shipping is cumbersome, e.g. a $200 bike that would cost $100 to ship. There's no fees. The downside is the people that don't show up so it can be a bit of a time suck.
Ebay works well for me for smaller bits, but they take a fee. I generally post with a high price and adjust it downward until finally someone bites.