Accomplish the indicated achievement to get the corresponding number of 
Gamerscore points:

Finder's Keepers (20 points): Find all 8 Items in a City Location in the 
Single Player or Co-Op Mission. 
Quick on the Draw (10 points): Find 3 items within 5 seconds. 
Bonus Plan (10 points): Find all 9 Bonus Items in one Mission. 
Not Impossible (10 points): Complete one Mission. 
The First Hint's Free... (10 points): Complete one Mission without using any 
Hints. 
Just Said "No" (25 points): Complete every Mission without using any Hints. 
Wham, Bam... (25 points): Complete a City Location in less than 30 seconds. 
Star Performer (25 points): Earn Elite Agent Rank in any Mission. 
You Always Remember Your First (10 points): Complete Mission 3 and capture 
Mister Smith. 
Back for Seconds (15 points): Complete Mission 6 and capture The Hammer. 
Third Time's the Charm (15 points): Complete Mission 9 and capture The 
Artiste. 
Fourth Down (25 points): Complete Mission 11 and capture Dr. Chaos.