In campaign mode on the sixth or seventh level, there is 
a capture the flag game. If you go directly right from 
your base, you will go over some mountains then see a 
stone structure. Go to it. Once there, you will find a 
laser rifle. From where you found the laser rifle, move 
down towards the enemy base. Go to the hills to the right 
of the base. You will have a very good perspective of the 
base. They might catch you and start going after you -- 
ski down the hill and use your get at the end of the hill. 
Go to the tower to steal their flag. Also, change your 
weapon when they find you (the laser rifle is poor at close 
range). Get to your base as soon as possible and score 2 points. 
You can do this repeatedly until time runs out.