The Krogan Sentinel, jack-of-all-trades, master of headbutting.
aka the quadruple threat 
Spurred by the recent thread on krogan melee, I have finally attempted a no-passives build on this guy; what I came up with surprised me in how many different ways it has to terminate foes.
I spec fitness for melee damage, and enhance this aspect with equipment, to get my rage going fast. Tech armor for more melee and more protection (and the occasional detonation to stagger mobs). Incinerate detonates the fire explosions set up by ammo (disruptor ammo/tech bursts would also work). The grenades hit like trucks (even if I use a cyclonic mod; a more expert player could increase their damage further by using a power amp); I use them to clear groups of unshielded mooks, soften more powerful units up before I wade in and melee everything, or to take down hp from bosses. Finally, the wraith holds an omni blade, extends my operative range, applies ammo well, and is capable of headshotting. It is easy to get four different kill medals with this setup without even trying (melee, headshots, tech, and biotic kills), an indicator of how varied this kit can be.
Maybe not the most efficient way to play, but a fun build that works well at close to medium range, and that offers a variety of gameplay options!
For Tuchanka!