“Pacer pissed off the Van Graff family big time. No one knows what went down, but word is the Van Graffs still want him dead.”— Rotface
Pacer is the right hand man of the King, who refers to him as "Pace." He helps to coordinate rule of Freeside from the King's School of Impersonation. Pacer and the King grew up together in the area, and having been through a lot together, the King trusts him, prefrequently giving him the benefit of the doubt.
Pacer can generally be found in the lobby of the School of Impersonation, but is also encountered around Freeside attending to his business during the course of several quests. He is generally abrasive in his interactions with the Courier. When paid for a tip, the Freeside vagrant Rotface will reveal that Pacer is a Jetaddict and suffers from a weak heart. This information is backed up by his medical records in the Old Mormon Fort. The medical record also lists various other pieces of information about him, such as his AB blood type and that he was either unsure or unwilling to share his last name and birthdate.
Birds of a Feather: Pacer, provided he's still alive, is one of the people The Courier must screen while guarding the door at the Silver Rush. When he walks up, Simon will say that Pacer is a troublemaker, but Pacer insinuates there's some sexual tension between him and Gloria Van Graff.
G.I. Blues: Pacer beats the NCR's envoy within an inch of his life, escalating tensions between the NCR and the Kings.
Kings' Gambit: The Courier is required by the NCR to kill or otherwise silence Pacer for spreading rumors about the NCR.
Effects of player's actions
After Birds of a Feather, one is able to tell Dennis Crocker there's bad blood between Pacer and the Van Graffs, opening up another route for the optional task of taking him out for the NCR during Kings' Gambit.
If the player character convinces the King to make peace with the NCR by means other than using the one favor he offers, Pacer stages a coup and dies in the gunfight between the Kings backing him and those that remained loyal to the King. There was an opportunity to pass a Speech check and convince Pacer to back down, but this was cut from the game. The King is devastated and mourns his loss, but carries on without him and goes ahead with the peace between the Kings and the NCR.
The Courier must talk to him to first gain access to the King. This can be done by either bribing him with caps, passing a 60 Speech check, or pickpocketing the key. If one elects to bribe him, their caps can be recovered in the subsequent conversation with the King by asking him if he always charges for an audience.
In Pacer's room on the 3rd floor of the King's School of Impersonation, there is a carton of cigarettes sticking out under his bed filled with his stash of Jet. By selecting the carton, one can either take the Jet or taint it and make it lethal if they have a Medicine skill of 60 or higher. This will only appear if one has obtained Rotface's tip and Pacer is sleeping or elsewhere.
Pacer is the only member of the Kings that has evil Karma and killing him results in good Karma.
Killing him before G.I. Blues is concluded, however, will result in that quest failing and Freeside Infamy being gained (along with the good Karma). Killing him after the completion of G.I. Blues will not in itself award Freeside Infamy, but if it's done when not hidden, nearby Kings will turn hostile and killing them will result in Freeside Infamy.
If the Courier has Cass as their companion, Pacer may ask her if he could give her a massage. Cass will reply that if he's looking for something to do, he should "put his head in the door and slam it, hard."
A height modifier of 1.05 makes Pacer almost 6'4" (1.92m) tall, making him one of the tallest human NPCs in the game along with The King. Only Jean-Baptiste Cutting and Lanius are taller.
↑The King: "Pace? He and I grew up together around here. We've been through a lot together, and there's no man I'd rather have at my side in a pinch. Don't judge him too harshly for trying to get some caps out of you. He probably took you for a squatter, looking for a place to settle down." (The King's dialogue)
↑J.E. Sawyer on Tumblr: "Jesse Farrell wrote the King, Pacer, a bunch of other Freeside and BoS folks (Hardin, McNamara). Jesse handled the setup of Rex, but I believe Jeff Husges did Rex's brain quest."