Sony let me unlock my Xperia Z. They also release the drivers to their hardware to the open source community. Well worth supporting this effort when you next choose a handset.
Oppo goes as far as supporting development of CyanogenMod and ParanoidAndroid ports for their devices and are releasing a device in partnership with CyanogenMod.
The Nvidia Shield is Nexus-level friendly: it's just fastboot oem unlock, no special keys or APKs or anything. It's also an incredibly nice device. (I wish Nvidia made phones...)
http://unlockbootloader.sonymobile.com/