We all have likes and dislikes according to aesthetics and other persuasions. What is your favourite - and if you like you most disliked - nebula, and for what reason? Can be diffuse, planetary, SNR or dark.
My personal all-time favourite, and the one I LOVE imaging is M78. A fascinating shape, wonderful dark areas superimposed with reflection glow and H-a and OIII regions.
Basically, not overly fond of just the H-a diffuse nebulae - I need the contrast of shapes and colours