The Lock
The Lock (ザ・ロック) is the stand of Tamami Kobayashi featured in Part IV: Diamond is Unbreakable.
Appearance/Personality
The Lock appears as a, simple enough, giant U-Shaped Lock hooked onto the target's heart. As with most Stands, only people with Stand powers can see it, even the afflicted has no idea it is there. It has no personality other than serving Tamami, and displays even little of that, seeming to have absolutely no personality. Tamami can also hold The Lock as a tangible item, as shown when he is called by Rohan Kishibe to confirm that Josuke is cheating in their game of dice.
Abilities
Guilt-tripping: By making someone feel guilt, Tamami can then summon The Lock and hook it to the person. Afterward, their guilt on it is multiplied continuously, represented by The Lock growing bigger and heavier, until the victim becomes so guilty they commit suicide. This does not even require the victim to be guilty about something they did, rather, he is able to make Koichi's mother almost commit suicide by making her feel guilty about her son.
Trivia
There is a concept which may be a reference to this stand in the popular DS series, Ace Attorney, called Psyche-Locks. They're similar in that they relate to the user's mental state and guilt.
References
