Teleport Partner Game

In this game you and your partner are trying to achieve some goal, and the only way to get through the trials is to, roughly, fire each other out of your guns. So, my gun fires my partner, and their gun fires me.

The original idea had some sense of "Maybe I'll purposefully dump you in the spikes so I get all the points to myself", or "Ok buddy, I pulled the lever and this place is sinking into the lava, get me out of here" "Nah..."

But I'm not quite sure how to work it so that both players aren't just trying to race to kill each other at the end.