Edit: Updated for Bangkok beta.
Due to the partial releases of Mafia Wars Moscow, the recent upgrades to some old equipment, and the several more expansions on the horizon, it seems like it would be a good idea to maintain a running "Best Of" list to outline the best offensive and defensive weapons, armor, and vehicles in game.
Note, to qualify for the list, it must be an item that drops from jobs (job mastery items (like the cazador assault rifle, godfather points items and limited edition items like the Red Coat will be excluded from the list).
Best Offensive Weapons:
Ubijca Assault Rifle: 43 attack, 18 defense - from the "Help "Plan" The Next Attack" job (Vory Only) in Episode 5 in Moscow.
Tanto: 43 attack, 28 defense - from the Yakuza Only Episode 5A, Chapter 3 job.
Best Defensive Weapon:
Cheng-Wei X94 Machine Gun: 25 attack, 45 defense. Sold in the Mafia Wars Bangkok faction store (Triad).
Best Offensive Armor:
Yakuza Assassin: 50 attack, 26 defense. Sold in the Mafia Wars Bangkok faction store (Yakuza).
Best Defensive Armor:
Shaolin Bodyguard: 27 attack, 51 defense. Sold in the Mafia Wars Bangkok faction store (Triad).
Best Offensive Vehicle:
Fugama Hasu: 46 attack, 23 defense. Sold in the Mafia Wars Bangkok faction store (Yakuza).
Best Defensive Vehicle:
Lloyds Spectre: 18 Attack 45 Defense - from the Yakuza only job in Episode 5B, Chapter 2 of Moscow.
Currently, most of the best items in game are now available in the Bangkok faction store. I am assuming there will also be some good drops from jobs in later episodes of Bangkok. More details to come.