If anyone asks me to suggest an anime, my first preference is always Code Geass. It has basically everything that baffles the viewers. the concept of establishment of world domination was weirdly great. Moreover, a character like Lelouch is very rare. This anime is going to give the viewers everything they want - action, psychological intellect, romance(a little suppressed though), trust issue scenes and scenes that will make anyone emotional. Needless to say, this anime is probably one with the best ending. Just give it a shot!