Racing Ghost

In Racing Games, you sometimes have the option of competing against yourself in Time Trial mode, not just by the final time, but by racing against a hollow "ghost" recording of a previous run. This might be your own run, your friend's, or even a stranger's downloaded from the web.

Some games have "staff ghosts" from the developers of the game, which may have to be unlocked first. Obviously, the developers' top record will be very difficult to beat, but not every staff ghost is like this. Sometimes, less gameplay-oriented members of the staff will provide a ghost, in which case out-racing this ghost might unlock a more difficult ghost.

In any case, ghosts provide an easy visual way to gauge one's performance without checking the clock.

Examples of Racing Ghost include:

F-Zero
Mario Kart
- The 7th game takes the concept pretty far. Every track has multiple staff ghosts (each unlocked after beating the last). If left in sleep mode, the 3DS will download ghosts from random players. There's an option to play against 7 ghosts at once. The Wii version also allowed downloads but had less ghosts per track at a time.
Mirror's Edge
Super Mario Galaxy has a literal ghost you can race against. There's also a sort of "cosmic" Mario (he's the same shape as Mario, but looks like a cutout into outer space) you can race against in a timed run of a given level.
In the Track Mania series, all opponents are always intangible ghosts: Your only enemy is the track itself.
At the beginning of the new Speed Racer movie, Speed races against his brother's time, and it's represented as a Racing Ghost.
Crash Team Racing
Some Need for Speed games have this.
Diddy Kong Racing (both versions) has a set of ghosts for each course as driven by T.T., a stopwatch character. Beating all of the ghosts unlocks him as a playable character.