@steemchiller is the first that comes to mind.

He is very underappreciated for the enormous service he provides for the community. STEEMWORLD is the most important app of them all in my opinion. Without it, I would power down and leave. I use it every day.

He is struggling to get paid the costs of the necessary server every month.
He can't even afford to run a witness server, because this would lose him 40 bucks every month in the beginning...