Donphan for nostalgia, but ground type is my favorite and the design is simple, looks tough and cool. It's debut in the Pokemon movie was also dope. Great tusk made my heart ink a little.
However, in recent years I have been liking Tangrowth, Alolan Ninetales, Mienshao, Tyrantrum, Hawlucha, Noivern, Mimikyu, Centiskorch, Skeliderdge, Glimmora, and of course Great Tusk, as I mentioned. All are just really fun to play around with and I've jived with the designs. They've also been on good teams that have given me success.
Tl;dr: Donphan
That was metal.