Preface: Texas A&M University was founded as a military academy in 1876. It remained an all-military school until 1962, when it began admitting non-regulated students.
Texas A&M University has some of the richest traditions in American collegiate history, from Bonfire and Midnight Yell to Ring Dance and Reveille. Here is one more: that of the phrase Gig 'em.
To "gig" someone means colloquially to point out their flaws. In straight military terms, it means to punish someone for unsatisfactory performance, and usually relates to dress code violations, a poor salute, or other small perfunctory errors.
The phrase became somewhat commonplace around campus, and by the early 1920s had been exported to the football games, where the 12th Man would yell, "Gig 'em, Ags!" Besides its presence at football games, it is used today almost exclusively as a close to a speech or letter ("Thanks and gig 'em").
If you want to make a lifelong friend, whenever you meet an Aggie, simply give them a thumbs up and say, "Gig 'em, Ags!"