I am looking for collaboration songs where Scandal sings together with other artists or provides the music. A recording of it (video or audio) should be available somewhere on the internet.

So far I have seen:
Scandal x Momoiro Clover Z - Ikuze Kaitou Shoujo
Scandal x Nanase Aikawa - Yume Miru Shoujo ja Irarenai  (my favorite so far, I am now also a fan of her music)
Scandal x Ryudo Uzaki - Rockn Roll Window
Scandal x Shoko Nakagawa - Don't say lazy
Scandal x Stereopony - DOLL
Scandal x Stereopony - Hitohira no Hanabira
Haruna  x Aqua Timez - Alones

If you know of any other such collaboration I would be very happy if you could name them.

(I am also actively searching so I will be updating my list when I find something and I  will add your additions as well)

SCANDAL X Keiko Terada from Show-Ya - Genkai Lovers ( they collaborated about 3 times,same song, pretty sure you can watch all of them)
SCANDAL X Kishidan - One Night Carnival ( performed this twice, both on Youtube)
SCANDAL x Ryudo Uzaki - Scandal Nanka Buttobase 

SCANDAL X Miwa X Yasuha Kominami - Rock n Roll Widow
SCANDAL X Kyoko Sekihara - Rock n Roll Widow ( They seem to never perform this song by themselves, huh? )
SCANDAL X TM Revolution - Shunkan Sentimental
SCANDAL X Tomomi Kahala × Kyoko Tomita - (M) -Princess Princess Cover (note: Rina's not on drums in this song, but she's there, if ya catch my drift .common.)

There are more collaborations but I can't seem to remember the Artists name. All the ones I've listed you can watch on Youtube, if not, another video site. But there's a 100% chance you can watch these.

Scandal x Mizca - Shoujo S (ANIMAX MUSIX 2010)
Scandal x Hiromi Go x Speed x Yoshioka Kiyoe (Ikimonogakari) - Otoko to Onna (Music Fair 2009.05.30)

SCANDAL × Fumiya Fujii - "Eros" (MUSIC FAIR)
SCANDAL × Hiromi Go - "Hollywood Scandal" (FNS Music Festival 2013)
SCANDAL × Ryudo Uzaki × miwa - "Rock 'n Roll Widow" (FNS Music Festival 2013)
SCANDAL × Shoko Nakagawa × NOKKO × Akio Dobashi - "Friends" (Bokura no Ongaku)
SCANDAL × Keiko Terada × Shin Domoto Brothers Band - "Genkai LOVERS" (Shin Domoto Kyoudai)
SCANDAL × Daisuke Asakura - "OVER DRIVE" (MUSIC FAIR 2013)
SCANDAL × Daisuke Asakura × NAOTO - "Kagen no Tsuki" (Bokura no Ongaku)
SCANDAL × Kaori Kishitani × Chisato Moritaka - "Sekai de Ichiban Atsui Natsu" (MUSIC FAIR 2015)
SCANDAL × Kaori Kishitani × Chisato Moritaka - "Watashi no Natsu" (MUSIC FAIR 2015)

Thanks a lot, I will check them all out.

Also Scandal x NEGOTO x Akai ko-en - (I Can't Get No) Satisfaction (BAND YAROUYO!!Vol.5 2014.03.16)