Go to Baron Von Brathaus (Y101) in Yucatan Casino. Grab the Mona Lisa painting by the front register and the other painting next to it. Grab the Servbot Mask on the table. Find a nearby zombie, and slam the Mona Lisa painting on it. Slam the other painting on it. Slam the Servbot Mask on it. Then, grab a Large Barrel outside Baron Von Brathaus, and slam it on the zombie with a hard attack to get the "Stick 'Em Up" achievement.