Instructions
Open "The Sims 2" and go into live mode.
Type "Ctrl" "Shift" and "C" to get to the cheat box, it will be located at the top of the screen.
Type in "UnlockCareerRewards" and hit enter.
Click on your Sim's profile and go to "Career Rewards." Locate the "Resurect-o-Nomitron" and place it somewhere on your lot.
Kill your Sim. Make sure to have more than one Sim on your lot who knows the Sim you just killed.
Have the living Sim use the Resurect-o-Nomitron, and place a bid to the Grim Reaper. If the bid is too low, the Grim Reaper will take the money and not resurrect the dead Sim. If the big is high enough, the dead Sim will return as a zombie in a cloud of red smoke.