The closest the fantasy gets to happening. A headset puts the horizon at your eye level, and the moment someone else's avatar is ten metres tall, the part of your brain that judges scale believes it. Nothing else on this site does that.
Most of this is VRChat. It was never built for size play and became the community's main platform anyway, because player scale is a setting. The worlds below add their own scaling, pickup and collision so that a tiny can be carried, climb, or be put in a jar. You need an account and a headset, or a PC in desktop mode for the worlds that allow it. The real-life guide covers doing this with a partner.
VRChat is the most-used size platform there is, by accident: avatar scale is in the player's hands. The built-in scaler stops at about five metres, and the size community has asked for more since 2023; these worlds carry their own scaling, pickup and collision systems to get past it.
Games made for a headset first. Games with a VR option are in the Games area with a [VR] badge: Giant's Sandbox and VRChat among them.
Worlds get rebuilt and unlisted without warning. If one of these has gone, say so and it comes off the list.