Boss TU-3

It may not be the prettiest tuner, nor the most compact, but it's everything a tuner should be. The strobe mode is incredibly precise. Sure, you have to tune one note at a time, but that is an old and proud ritual, one that only this pedal will make enjoyable.
Don't quote me on this, but it will even make you sound better (at least in tune anyways).

Pros:
Robust, as all Boss pedals are. I expect my great grandkids to still use this pedal while touring the icy moons of Saturn.
It allows the reference frequency to be adjusted, for all you A=432 enthusiasts.
It takes literally no space in your power station, really! It even says "9V DC out jack" in the top of the pedal. Go check it if you don't believe me!
Can be run in bypass mode or you can have a mute switch for free! I don't know you, reader, but you look like someone who would love to have a mute switch for free that has fun lights and stuff (also tunes).
It has buffered bypass and typically goes at the start of your pedal chain. That's just smart thinking. Thank you Boss!
Also in black (they sound the same).

Cons:
None (It's true).