As of this moment, Toronto FC are the only team in MLS that plays as a 4-4-2 diamond formation, although Seattle and Orlando could make the switch sooner rather than later. They use this formation to both get Sebastian Giovinco in a position to do the most possible damage (second striker) and to get as many offensive talents as possible on the field. It's worked to perfection over the last few weeks — although they did play a 5-3-2 against New England last week — and they've won four straight matches.
The pure amount of attackers Greg Vanney has at his disposal rivals that of any other team in the league: Giovinco, Jozy Altidore, Tosaint Ricketts, Jay Chapman, Marky Delgado, Jonathan Osorio, the injured Daniel Lovitz, Tsubasa Endoh, Mo Babouli, and Jordan Hamilton all have had roles in various places in the attack this season, and this isn't even mentioning their other starting-caliber midfielders: Michael Bradley, Benoit Cheyrou, and Will Johnson (who is currently injured).