The Tankiest Assassin
I introduce to the world, the tankiest assassin, Nocturne! 
This is the build I used. http://imgur.com/NpKNeFL.png
Nearly unkillable and still getting one shots.
The only weakness, which is a huge one in this current meta, is lethality.
Although it doesn't matter how much lethality they have if they die in less than a second.
Link to game: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2431051195/233333966?tab=overview