Certainly, there are several over-the-counter serums that can help with dark spots. Here are some top picks based on their active ingredients and their effectiveness.

1. Vitamin C Serums: Vitamin C is a potent antioxidant that can neutralize free radicals. It also helps your skin's natural regeneration process, which helps your body repair damaged skin cells. A popular choice is the "SkinCeuticals C E Ferulic" which combines Vitamin C with Vitamin E and Ferulic acid for enhanced results.

2. Retinol Serums: Retinol is a derivative of Vitamin A and is well-known for its ability to speed up skin cell turnover and promote collagen production. This can help fade dark spots over time. "Neutrogena Rapid Wrinkle Repair Serum" is a widely available option that combines retinol with a glucose complex and hyaluronic acid.

3. Niacinamide Serums: Niacinamide, also known as Vitamin B3, is a powerful ingredient that can reduce inflammation and hyperpigmentation. "The Ordinary Niacinamide 10% + Zinc 1%" is a popular and affordable option.

4. Alpha Hydroxy Acid (AHA) Serums: AHAs like glycolic acid and lactic acid can help exfoliate the skin and reduce the appearance of dark spots. "Drunk Elephant T.L.C. Framboos Glycolic Night Serum" is a high-quality AHA serum.

5. Hydroquinone Serums: Hydroquinone is a strong skin-lightening agent and can be very effective for reducing dark spots. "Murad Rapid Age Spot and Pigment Lightening Serum" is a well-known product that combines 2% hydroquinone with glycolic acid.

Remember, it's important to use these products as directed and always wear sunscreen during the day, as many of these ingredients can make your skin more sensitive to the sun. Also, everyone's skin is different, so what works for one person may not work for another. It's always a good idea to patch test a new product before applying it to your entire face.