Hi, me again!
After discussing it a bunch with @Tetchta
when he was making his, I decided to go ahead and finish mine as well. Except rather than Halo sounds (heathen), mine uses the original ones from Unreal Tournament. Multikills are the same amount as UT (mostly for stuff like calamity, oblivion, etc. It's not on a timer like Unreal's), Killing sprees are adjusted a bit to make them realistic to achieve.
Mine also tracks other people's kills, as well, not just your own. If you don't wanna do that, just disable the trigger for it and it'll still track yours. Otherwise it's plug-and-play just like his one is; install it and you're good to go.
It will automatically reset ~30 minutes after the last kill happened. People's sprees also reset if they die.
Demonstration:Download from here!