Some of my personal favorite leads are Metagross and Snorlax. Metagross is nice to see what your opponent's best physical tanks are.
I used to lead with TrickBand Alakazam and always start off with Focus Punch. I also have no qualms about leading with Blissey either in DP or RSE, it's one of those leads that isn't very easy to beat unless you are like CB Tyranitar, and even then the threat of Counter can keep those in check. I think it's incredibly hard to lead with Suicune and expect a sweep, though.