I hope they put different skulls for different kill types (number of people killed on multikill=number of skulls displayed, snipes have a little "X" at the top of the skull, assassination type kills have ninja skulls, etc). Oh yeah, and hopefully you get cash for achievements, or special armor for specific achievements. That would be awesome.
Player 1 gets a Reign of Terror, he is now the walking Ring of Fire. Player 1: "AAAAHHH!!! #$%^$$!!!"
The two guys watch Player 1 run around like a chicken with its head cut-off.
Player 2: "OMG! that ****er is on firah!!!" Player 3: "He's abusing the Warp Pistol! he SHOULD be flaming like ****!"
Player 2 gets a 3 kill streak
Player 3: "Stop stealing my god damn kills!" Player 2: "AH!!! i cant shoot! theres flames on my hands! i cant see!!!" Player 3: "lol"
Yeah, that would be funny, but I was thinking more along the lines of showing who is hot (like some forums do with "hot" threads). No damage to the "hot" player (unless they set it up so if you get too hot, you need to keep killing to stay alive). Likewise, if someone goes on a death streak of three deaths in a row (without any kills), they should look like they are inside an ice cube.
And you have a point multiplier based on the streak. Kill someone on a 2 kill kill streak and you get 1.2 point. 3 kill kill streak would net 1.3 points, etc. Of course, kill someone that's died twice in a row and you only get .8 points.