This is a fantastic question! And I love your sentinel. The colour scheme is an inspired choice.
For me it’s my Dwarf Miners from Battle For Skull Pass. They had been in the pile of shame since my first day in the hobby, and finally getting them finished is a matter of great pride for me.
They were also joyous to paint, the simplicity of the models was just so refreshing and it’s one of the highlights of my whole hobby career so far.
Link to more pictures in my BATG entry for these models.