Gundam girls and other MS girls, share if you want.
Funfact: Gundam/MS Musume (Gundam/MS Girls) existed before mecha musume (Mecha girls, which would actually include Gundam Girls), and deserve an own term because they predate mecha musume by nearly 2 decades.
Yes, its by CLAMP, to honour the most epic Gundam battle scene in their opinion. Nobuhiro Watsuki (Kenshin), GACKT, people working at Square Enix and many others second that.
Wing Gundam Zero EW ver. ("Wing Zero Custom")
Strike Freedom Gundam
Heine's Custom Zaku
Principality of Zeon MS (plus an Asshimar, thats actually Titans)
I personally like the last two best in a visual. Though have to say I never would have expected someone to create such beautiful artworks out of Baund Docs.
Of course, Nu Gundam/Amuro/Sakura hybrid has its own level of omake awesome.