Death

Death is a state in which a Sims dies.

Grim Reaper
The Sim in question is visited by the anthropomorphic personification of the Grim Reaper who plays a cameo depending on the method of death and the aspiration level of the Sim in question. Sims can be killed in many ways including fire, shock, starvation, flies, being eaten by the cow plant and being scared to death. If there is a living sim around they can plead for their loved one with the Grim Reaper but it doesn't always work. The chances of success are determined by the relationship of the sim with the nearly deceased and pure chance.

There is a different animation for pets that die.

In The Sims 2: University there is a special item, the Resurrect-O-Nomitron which can restore Sims but for a hefty fee of up to §10,000. If the Sim who wants to bring another Sim back pays very little the Sims will return as a zombie, with reversed skills or not at all. Except for children.

If no one is around when the Reaper comes to call Death stays on the lot for a little while, uses the toilet and watches TV.

Finally if the Sim that died is the last Sim on the lot an amusing dialogue will appear.

The Sims

 * Starvation: If a Sim doesn't eat for a prolonged period of time (several days), they will starve.
 * Drowning: If a Sim uses a pool without a pool ladder, they will eventually use up their energy and die.
 * Fire: When a Sim caught fire for a period of time, they will die by fire.
 * Electrocution: If your Sim isn't so good at Mechanical and tries to repair broken electric items or is struck by lightning, he/she may die.
 * Virus: After playing with a guinea pig from a dirty cage, the Sim may be infected by virus and will die if not treated well.

The Sims 2

 * Starvation: If a Sim doesn't eat for a prolonged period of time (several days), they will starve.
 * Fire: If a Sim with a low cooking skill cooks a meal there is a chance it will catch fire. Similarly if the food is left in the oven by a careless Sim or, very probably, a Nanny, the food will also catch fire. If there is no fire alarm present it is up to the Sim to put out the fire. This can be done by calling the fire department or by clicking on the fire and choosing 'extinguish'. There is no way to buy a fire alarm while the fire is there as build mode and buy mode are disabled. The longer a Sim is in proximity to the fire (and because all Sims are autonomously brought to the fire to insist the 'panic' action they will be) the greater the chance is that they will catch fire. When three of there motives are completely depleted the Sim will die.
 * Drowning: If a Sim uses a pool without a pool ladder, they will eventually use up their energy and die.
 * Flies: If a lot is messy with many fly-infested objects, there is a chance all the lots flies could form a killer swarm when a Sim steps over a fly-infested object and eat the sim alive.
 * Fright: If your Sim sees a ghost, his/her motives fall drastically. If the critical needs (hunger, energy, etc.) fall far enough, the Sim will die.
 * Satellite: While watching clouds (daytime) or stargazing without the telescope (nighttime), there is a very remote chance that a satellite will fall on your Sim. The satellite can be sold in buy mode, but it devalues quickly, so waste no time, sell it right away.
 * Sickness: If your Sim gets ill and isn't cured on time, he/she may die, but usually if you let them relax, they will get better.
 * Electrocution: If your Sim isn't so good at Mechanical and tries to repair broken electric items or is struck by lightning, he/she may die. Unless the Sim's needs are all in the green, this is usually fatal.
 * Old age: When a Sim reaches the end of their life, they will die of old age. This is the only time in which a living Sim will not be able to plead with the Grim Reaper to bring the Sim back.

The Sims 2: University

 * Cowplant: Available with The Sims 2 University only. If a Sim attempts to 'take the bait' the hungry Cowplant offers, they will be eaten.

The Sims 2: Nightlife

 * Sunlight: When a vampire Sim stays in the sunlight for too long, he or she will die.

The Sims 2: Open for Business

 * Rally forth: Doing the rally forth interaction while needs are low.
 * Elevator: If the elevator breaks down while Sims are in it, and their needs fail, then they will die.
 * Evil Kite

The Sims 2: Seasons

 * Freeze: If your Sim spends too much time outside in the winter, first he/she will freeze, and the longer they remain frozen, the worse they get. At the end, they die.
 * Heat: If your Sim spends too much time outside in the summer, they will suddenly catch fire and die.
 * Hail: When at least 4 needs drop below 50% while standing in hailstorm, your Sim will die.
 * Lightning: When a lightning hit a Sim when he or she is using a hot tub, he or she will die.