Epsilon-Tex: Tex used her knife to parry against the blade of the Meta's brute shot and stabbed him in the back before the Meta captured her.
Washington: Wash obtained Tex's knife in n+1 and used it to wound the Meta, causing him to cloak and attempt an ambush. Wash, however, saw through his invisibility and threw the knife directly into his shoulder. He also used a knife he stole from Felix to assault Locus in a similar manner.
Girlie: In Season 10, this Insurrectionist wielded several custom made combat knives against Carolina. Her weapons were unique, having very long curved blades similar to a kukri as well as being decorated with hearts.
C.T.: C.T. made use of a combat knife to even the odds against Tex and Carolina. She was eventually disarmed by Carolina and killed by Tex.
Simmons: In the PSA, Drafted, Simmons assassinates an alien using this weapon while using an analogy to remember how to do so.
Felix: When a Fed tries to ambush Felix from behind, the latter quickly throws a combat knife into his face, before striking a pose and saying quietly to himself, "I am fucking awesome!" Felix later uses this weapon in a battle with Carolina, using it to stab her in the leg. Toward the end of Season 12, he goes on to stab Tucker with it. Later on, towards the end of Season 13, Felix uses multiple throwing knives against Washington.
Buckey: Buckey uses a combat knife to kill a UNSC soldier during the beginning of Season 15.