There are many brands of keycaps in the market, each offering their own unique designs, materials, and profiles. However, some of the most popular brands of keycaps among keyboard enthusiasts and gamers include:

1. GMK – A German brand that produces high-quality keycaps with vibrant colors and sharp legends. GMK keycaps are known for their durability, compatibility, and customization options.
2. Tai-Hao – A Taiwanese brand that offers a wide range of colorful keycap sets with unique designs and patterns. Tai-Hao keycaps are known for their affordability, durability, and compatibility with most mechanical keyboards.
3. Ducky – A Taiwanese brand that specializes in mechanical keyboards and accessories. Ducky keycaps are known for their high-quality construction, durability, and customization options.
4. Signature Plastics – An American company that produces a variety of keycap profiles and designs, including the popular SA and DSA profiles. Signature Plastics keycaps are known for their high-quality construction and customization options.
5. PBT – A material used by many keycap brands for its durability and resistance to wear and shine. Many keycap sets use PBT plastic for their keycaps.

Ultimately, the most popular brand of keycaps will depend on personal preferences and needs.