Ubisoft have given the Assassin's Creed II community the power vote on an achievement / trophy to be included in the game. The four choices are pretty standard achievements and are as follows:
The taste of revenge - Kill X Brutes (heavy guard)
Weapon Master - Use all weapons at least once
Victory lies in preparation - Get all available upgrades for Ezio
Mighty traveler - Travel X kilometers within the game
You can vote on the official website or at the Assassin's Creed facebook page.