No offense, but you people are scaring me.
QUOTE(Harros)
I had this same problem. Kills score is not 1 for 1. It is the actual point value of the unit being killed so for example a zealot would be 200. A marine would be 100. It is whatever the (I believe default) cost (Haven't tryed changing the cost of the units yet) of the unit is times 2. You can see this is you say display leaderboard for kills.
The point kill score value is preset in the units.dat file. Seriously.
QUOTE(Harros)
But hes looking for 1 kill = 1 mineral.
The onyl way to set this up with the Kills thing is find out the point value of all the units, then set up some switchesthat determain how much to subtract.
EX:
Con:
Currentplayer kill score is at least 200
Switch Zealot is set
Actions:
Subtract 200 Kill score
Add 1 to custom
Add 1 to minerals
preserve trigger
***
Con:
Currentplayer kill score is at least 100
Switch Marine is set
Actions:
Subtract 100 Kill score
Add 1 to custom
Add 1 to minerals
preserve trigger
Here's a not foolproof but really good way used in many defense maps:
Conditions:-Player kills score is at least 50
Actions-Set player kills score to 0
-Add 1 custom to currentplayer score.
Hypertrigger it, and it will work better. Now your kills is your custom score value.

[EDIT] Hmmm. Upon closer look, it's just Harros that scares me. I'm feeling better that Yoshi knows this.

50 works better than 1 because otherwise (even with hypertriggers) you could have an overlap.[/EDIT]