Here is the full list of all 26 Call of Juarez: Gunslinger achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Collect all Nuggets of Truth.
Win a duel honorably in under 0.6s.
Complete the Story on hard difficulty.
Complete the Story on True West difficulty.
Forgive your lifetime nemesis.
Kill a shotgunner with a close-range shotgun blast.
Kill a bird during a winning duel.
Complete all Arcade missions.
Get all Arcade Mode stars.
Shoot a flying stick of dynamite and the one who threw it on a single Concentration.
Score the maximum of 3 stars in any Arcade mission.
Fight in Concentration for 15 minutes.
Complete the duel challenge, winning all duels honorably.
Unlock all skills in Story Mode.
Complete the Story on any difficulty.
Kill your lifetime nemesis honorably in a duel.
Find and kill Jim Reed.
Reach combo level of 20.
Unlock both exclusive weapons in a single category of skills in Story Mode.
Discover a shipwreck in the Missouri swamps.
Find and kill Johnny Ringo.
Find all Nuggets of Truth in a single mission.
Shoot through a hole to kill an enemy that hides behind a shield.
Give it to them straight about your meeting with Pat Garrett.
Kill 5 enemies when falling down through the air.
Unlock a skill.