The SIG Sauer P229 is a compact, German/Swiss-made firearm favored by John Casey. It is designed specifically for concealed carry situations.
Casey notably uses the P229 throughout the majority of Team Bartowski missions, including in "Chuck Versus the First Date", when General Beckman orders him to assassinate Chuck. Casey's P229 is modified over the standard production variant, with Crimson Trace laser grips and mounts for a suppressor; which are utilized during "Chuck vs. The First Date".
Chuck receives his very own P229R in "Chuck Versus the Final Exam" by courier the following morning after completing his "red test", on becoming a full fledged CIA agent. This is the weapon he uses to kill Daniel Shaw in "Chuck Versus the Other Guy" and is seen again in "Chuck Versus the Ring: Part 2" as he walks into the Buy More before their final confrontation.