I am looking for a microcontroller that is small (like a attiny10) which is the smallest one I could find. Requirements I need: analogRead on 1 pin, 7 pins for analogWrite to micro leds so in total 10 pins (ground, power, analogRead, analogWrite). It's circuitry has to be basic no adding extra things like a crystal oscillator etc.. This will allow me to send a certain code to the recieving pin and then the microcontroller decide which led to turn on.
I made a Arduino develop board with ATtiny3217, it has a 24-pin VQFN form factor, but as powerful as ATmega328p, with no external crystal and capable running at 20MHz.
If this is not suitable for you, look into the new tinyAVR family, they are the new generation of ATtiny with more functionalities than the older ATtiny family with the smaller footprint.