A while back Bungie.net, the makers of the Halo series of games, started tracking data on their servers about how their different online multiplayer maps are preforming. They converted the data on kills and deaths in the multiplayer games into heatmaps, and then started publishing the maps online for everyone to see.
The advantages to players are that you can see places to avoid (areas with the highest deaths), and the locations from where the most kills come from. The map above shows the total data for the map called The Pit. But you can narrow down the information based on the type of weapon used. For example the map below shows the locations of the kills made with the sniper rifle. Meaning that shooting from these locations have been the most successful. (Also helpful if you keep getting killed by snipers and can't find them)
"Heatmaps are the Doppler Radar System of Death in Halo 3. We're tracking encounters, weapons used and their results in a given game, collecting that data and sharing it with players visually. The key here is 'the darker the red, the more frequent the deaths (or kills, depending on the parameters)'," Bungie explains in its weekly update.