This is my preferred list, though usually I try (and don't always succeed) to focus on rosters, and customize each list depending on the scenario and opponent. Most of my lists end up being a variant of this (one way or another) if I'm going up against MEQs. If I'm going against hordes, I'll probably drop the plasma and one of the missiles, and throw down some more bolters (yay bodies). I love sniper on the plasma for the rerolling of 1s in particular. Pretty safe to overcharge that way.
+ Leader +
Intercessor Sergeant: Bolt rifle, Leader, Power sword
+ Specialists +
Reiver Sergeant: Bolt carbine, Combat knife, Veteran
Tactical Marine Gunner: Plasma gun, Sniper
Tactical Marine Gunner: Demolitions, Missile launcher
+ Non-specialists +
Scout Gunner: Camo Cloak, Missile launcher
Scout Gunner: Heavy bolter