Both, but also just like, one person being mesmerized by the beauty/deadliness of the gun in question. Like sort of terrified boner without the terror or the jokiness. For instance, McCree getting off to thinking about how deadly Gabe is with his guns, how easily he could get killed by them if Gabe was interested in doing so. Just arousal at how gorgeous/deadly they are, both just as guns or in Gabe’s hands specifically.