Pacer is the right hand man of The King and helps to coordinate rule of Freeside from The King's School of Impersonation. The King's good nature ignores Pacer's continuous misbehavior out of respect for their childhood friendship, and only rarely speaks ill of him. 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.
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.
After Birds of a Feather, you are 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.
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 you chose to bribe him, you can recover your caps in the subsequent conversation with the King by asking him if he always charges for an audience.
If you are low on caps, and you need to see The King, move between the door and Pacer, pickpocket him (doesn't matter if you are hidden or not) and open the door quickly before he takes the key back. He and the Kings will not attack you.
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, you can either take the Jet or taint it and make it lethal if you have a Medicine skill of 60 or higher. This will only appear if you have Rotface's tip and Pacer is sleeping.
Killing Pacer results in good Karma due to his evil personality.
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, it's likely nearby Kings will become hostile, and killing them will result in Freeside Infamy.
If you have Cass in your party, Pacer might 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."
Pacer is the only member of the Kings that has evil Karma.