Drop the bomb in de_map or Demolition. Keep buying primary weapons during the warm-up period for a match. You will toss the weapon you currently have equipped on the ground, which is usually picked up by players who have not purchased a weapon or have just spawned in. Secondaries will not work because the other players must manually switch to it from their starter pistol. Purchasing cheap primaries like the MP7 allows you to get the most out of your money.