Genie's lamp

When a Sim cleans the Antique Lamp introduced in Livin' Large, a genie will pop out and grant the Sim a wish once a day. Once a wish has been made, the lamp can no longer be sold for its full value, even if it is being sold on the same day it was bought.

The Sims 2: FreeTime
In The Sims 2: FreeTime, the Dusty Old Lamp may be delivered by the Gypsy Matchmaker. Until a Sim has rubbed the lamp, it can be sold by clicking on it and selecting "Sell Lamp", but it cannot be sold in Buy mode. Once it has been rubbed to summon the Genie, it cannot be sold. Once three wishes have been made, the lamp will disappear.

The Sims 3: Showtime
In The Sims 3: Showtime, the Dusty Old Lamp may be found while exploring the catacombs in a graveyard. It may also be obtained after giving a "legendary" stage performance or traveling through a Plasma Punch Gyroscopic Conductor's dimensional gate. It may also be bought for 30,000 Lifetime Happiness points.