Killionaire

Killionaire is a multikill medal awarded in Halo 3 Multiplayer for killing 10 opponents within 4 seconds of the previous kill, this medal is represented as a black hexagon with 10 platinum/silver stars. Unlike Halo 2's "Killimanjaro" medal, this does not repeat if you kill 11+ opponents withing 4 seconds of the previous kill. This is the hardest of all multi-kill medals to achieve. However, when Bungie opened up the Grifball playlist on March 6, the medal became much easier to achieve, this can also be more easily achieved through using Team Swords on Multi-Team. This multikill medal is actually shown in the "special" medals row, instead of the "consecutive kills" medal row.

An easy way to obtain this medal is by setting up a forge map with one spawn spot and a wraith, just keep firing the main turret and you can get many kills in a row.