Davey has appeared as a guest vocalist on releases from various other bands, including:
Background vocals on Tiger Army's Tiger Army, Tiger Army II: Power of Moonlite, Tiger Army III: Ghost Tigers Rise under a different name and Music from Regions Beyond.
The Transplants song "Quick Death" from their self-titled album.
The Nerve Agents track "Jekyl and Hyde" from their second release, Days of the White Owl.
Backing vocals for The Offspring albums Ixnay on the Hombre and Americana.
The Dance Hall Crashers song "I Don't Wanna Behave", from the album Lockjaw.
The Fury 66 track "Blue Strip".
The Heckle cover of The Misfits song "Astro-Zombies".
Havok also appears on Bleeding Through's DVD, Wolves Among Sheep.
Havok is seen on the Eighteen Visions's CD/DVD while recording their self-titled album.
Havok sang a duet with Billie Joe Armstrong twice on Green Day's 2nd leg of the North American 21st Century Breakdown Tour, which is rumored to be on the next Green Day live album.
Sang the Operation Ivy song "Knowledge" with Tim Armstrong and "Radio" with Rancid on the Give 'Em the Boot DVD.
Voice featured, along with other hardcore punk luminaries, in an answering machine recording on the All Bets Off album, "Girls About Songs".
Sang a cover of "Straight Edge Revenge" by Project X alongside the hardcore punk band Ceremony on November 6, 2008 in Berkeley California.
Featured vocals in the Scarlet Grey song "The Sky & I" on their album Fancy Blood.
"Smile and Nod" by The Dear & Departed.
Several live guest performances doing cover songs with Los Angeles band Pop Shop.
"S.K.Y." by The Witch Was Right.
Some of Davey's acting roles:
1997 - Mary Jane's Not a Virgin Anymore [George]
2003 - Clandestine [himself]
2006 - Live Freaky! Die Freaky! [Hay, Voice acting]
2009 - Godkiller: Walk Among Us [Dragos, Voice acting]
2011 - American Idiot musical [St. Jimmy]
Tim Timebomb's RockNRoll Theater [Devil]
2012 - Knife Fight [Jimmy McSorley]