Determining the “best” custom logo design service can be subjective and depends on your specific needs, preferences, and budget. However, I can provide you with a list of reputable logo design services and agencies known for delivering high-quality custom logos:

1. 99designs (99designs.com): 99designs offers a platform where you can start a design contest, and multiple designers submit logo concepts based on your design brief. You choose the winning design from the submissions.
2. Looka (looka.com): Looka, formerly known as Logojoy, provides AI-powered logo design services. You can create a custom logo by entering your business details and preferences.
3. Designhill (designhill.com): Designhill is a platform where you can launch a logo design contest, work with freelance designers, or use their AI-powered logo maker tool.
4. Hatchful by Shopify (hatchful.shopify.com): Hatchful offers a free online logo maker tool with customization options. It’s suitable for small businesses and startups.
5. Tailor Brands (tailorbrands.com): Tailor Brands combines AI and human designers to create custom logos. They also offer branding packages.
6. LogoMakr (logomakr.com): LogoMakr is an online logo maker tool that allows you to create custom logos by choosing from a library of icons and fonts.
7. Canva (canva.com): Canva offers a user-friendly online design platform with logo templates that can be customized to create custom logos.
8. Fiverr (fiverr.com): Fiverr is a freelance marketplace where you can hire individual logo designers. You can browse designer profiles, portfolios, and reviews.
9. Upwork (upwork.com): Upwork is another freelance platform where you can find and hire individual logo designers. You can post your project and receive proposals from freelancers.