Pimoroni Pico HAT Hacker
Pimoroni's Pico HAT Hacker gives you full access to all 40 pins on your Pi, broken out at the top. It's a super-skinny 0.8mm PCB, so you can solder it right onto the pins on your Pi and still have enough height on a standard header to fit a HAT or pHAT on top.
There are handy labels for all of the pins, with BCM pin numbering on one side, and more descriptive labels on the other to show where the I2C, UART, SPI, PWM, and I2S pins are. You can solder the Pico HAT Hacker either way up, depending on which set of labels you find more useful.