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

Jump On (10 points): Perform 50 Perfect Jumps.
Bridle Shower (10 points): Fall from the horse into the water.
Lucky Horseshoe (10 points): Complete a Perfect Round.
Seventh Wonder (15 points): Perform 7 Perfect Jumps in a single ride.
Pony Express (20 points): Win Gold medals in the 7 standard Horseback Riding challenges.
The Reinmaker (30 points): Win Platinum medals in the 7 standard Horseback Riding challenges.
Blazing Saddles (40 points): Win Diamond medals in the 7 standard Horseback Riding challenges.
Hang 10 (10 points): Fly at more than 95 mph continuously for more than 10 seconds.
A Perfect 10 (10 points): Fly through 10 Perfect Rings in one ride.
Cool Hang Luke (5 points): Complete the challenge without the help of thermals.
Human GPS (5 points): Collect all Secret rings in every challenge.
Golden Eagle (20 points): Win Gold medals in every Hang Gliding challenge.
Air Baller (30 points): Win Platinum medals in every Hang Gliding challenge.
This Is Forever (40 points): Win Diamond medals in every Hang Gliding challenge.
Bulldozer (10 points): Score a Touchdown doing all stiff arms and without jumping.
Born to Be Wild (15 points): Score 3 Perfect Touchdowns in a row in the Running Back challenge.
Three Is Company (10 points): Perform 3 Perfect Throws in a single challenge.
Robin Hood (10 points): Score 3 Perfect Centers in Target Throw.
Gold Rush (20 points): Win Gold medals in every Football challenge.
Gridiron God (30 points): Win Platinum medals in every Football challenge.
A Girl's Best Friend (40 points): Win Diamond medals in every Football challenge.
The Untouchable (10 points): Finish a round without getting punched.
Blowing It (15 points): Land at least 85% of your punches in a single match.
Sting Like a Bee (15 points): Win the bout in less than 1 minute.
Rubber Wall (10 points): Finish a whole boxing match parrying all punches.
Round Up (20 points): Win Gold medals in every Boxing challenge.
Just Beat It (30 points): Win Platinum medals in every Boxing challenge.
ADRIAN!!! (40 points): Win Diamond medals in every Boxing challenge.
Cleaning the Cobwebs (10 points): Win a penalty shootout challenge scoring all your goals in the Top Corners.
William Tell (10 points): Complete the Target Shooting challenge hitting more than half the targets.
Sniper (10 points): Finishing the Scoring Zone challenge with at least four 100-pt shots.
Hurricane (15 points): Score on your first attempt in all wind rounds in the Midfield Kick challenge.
24-Carat Goal'd (20 points): Win Gold medals in every Soccer challenge.
Field of Dreams (30 points): Win Platinum medals in every Soccer challenge.
Shine On (40 points): Win Diamond medals in every Soccer challenge.
Go Ahead and Jump (10 points): Jump 784 feet in Ski Jump.
Run Like the Wind (10 points): Ski at 68 mph for 10 seconds.
Heaven's Gates (10 points): Finish a Super G race without touching any gate or fence.
Demolition Derby (10 points): Hit other skiers 5 times.
Golden Child (20 points): Win Gold medals in every Ski challenge.
Avalanche (30 points): Win Platinum medals in every Ski challenge.
Ice Flakes (40 points): Win Diamond medals in every Ski challenge.
Almost Famous (10 points): Take 3 Pictures at end of the Welcome Tutorial.
States Invader (20 points): Become a National Champion in any sport.
Napoleonic Complex (25 points): Become an International Champion in any sport.
Who Can Icon? (30 points): Become an Icon in any sport.
I Am Legend (40 points): Become a Legend in any sport.
Meet Your Maker (5 points): Watch the Credits without skipping them.
Look at You! (25 points): Appear on 6 different International Magazine Covers.

Additionally, there is one secret achievement:

We Love You (50 points): Congratulations from the Dev Team! You won Diamond medals in every Challenge for every sport!