It is possible to glitch Phasewalk such that a weapon is held while Phasewalking. One benefit to this is that the glitcher can immediately fire their weapon upon exiting Phasewalk, instead of having to pull out their weapon (delaying shooting by a flourish).
Depending on a variation in the method of glitching Phasewalk, the Siren player can be visible while Phasewalking or invisible, as normal.
Phasewalk is glitched by opening a character menu (such as map, XP tab, inventory, etc.) while or within milliseconds after activating the action skill. Normally, a character menu forces Phasewalk to end. The menu must be kept open for at least 100 ms, or else the Phasewalk will continue as normal. If the character menu is closed between a minimum of 100 ms and a minimum of 550 ms for glitching Phasewalk invisibly, Phasewalk will be glitched visible. Glitching Phasewalk, in this way, is only possible when the glitcher is not the host; when playing in someone else's game.
It is possible to glitch Phasewalk as the host by perfectly timing the drop of a weapon simultaneously with the activation of Phasewalk. I don't know if it's ever possible to shoot while Phasewalking as the host.
Glitching Phasewalk soon after joining a game doesn't allow shooting while Phasewalking. Something eventually toggles such that afterwards, glitching Phasewalk also allows the glitcher to shoot and throw grenades while Phasewalking. Such toggle lasts for the rest of one's stay. I've tested thoroughly, but have found no independent variable which noticeably corresponds or correlates to the toggling; it seems random over time.