[Android One (First-Generation) Cross-Device Origin] meprakash_pyc:
3. Custom ROM, GAPPS, Kernels & Xposed for Marshmallow 6.x.x

A. Marshmallow 6.x.x Based Custom ROMs

1. OCT_OS: Visit xda thread from here

2. CyanogenMod (CM) 13 [Unoficial]

a) By Swapnil: Visit xda thread from here

b) By Ujwal:

Build1: Visit xda thread from here

Build2: Download from here

3. CyanogeMod (CM) 13 Official Nightlies/Snapshots by Varun Chitre: Visit xda thread from here

4. OMNI ROM

V6.0 AOSP: Visit xda thread from here

V6.0.1 HomeMade: Download from Basketbuild

5. crDroid Android: Visit xda thread from here

6. Tesla OS V3.0 Based On CM13: Download from here

7. AICP 11.0 | Nightlies Build: Visit xda thread from here

8. Dirty Unicorn (DU) V10.0 Dirty Deeds

Build Date: 20151111Download from here

Build Date: 20151210 Download from here

9. NuSlim-sprout4-6.0..0.1-UNOFFICIAL: Download from here

10. Euphoria-OS-6.0-sprout4-UNOFFICIAL-20151115: Download from here

11. Pure_Nexus_Sprout4-6.0.1: Visit Xda thread from here

Build Date: 20151208 Download from here

Build Date 20151222: Download from here

12. Resurrection Remix ROM Based on MM

RR-M-v5.6.0-20151210 By Bu Bun: Download from here [Use Banks GAPPS from here]

RR [OTA Enabled] [6.0.1_r3][OFFICIAL]: Visit xda thread from here [Use Banks GAPPS from here]

13. CM 13.0 Temasek by Bun Bun 20151214: Download from here [Use Banks GAPPS from here]

14. AOKP_sprout4_mm_unofficial_2015-12-14_17: Download from here [Use Banks GAPPS from here]

15. Operation MONARCH v1.0: Visit xda thread from here

16. Team UB [6.0.1]: Visit xda thread from here

17. MOKEE Official Nightly: Visit xda thread from here

18. Cyanpop v4.5: visit xda thread from here

19. [6.0.1] Zeus-ROM | Beta 1 [25/12/2015]: Visit xda thread from here

20. [ 6.0.1 ] SAOSP - M: Visit xda thread from here

21. [MM/6.0.1] BeanStalk 6.03: Visit xda thread from here

22. [ROM][6.0.1][UNOFFICIAL][SPROUT4] Paranoid Android 6.0.2 : visit xda thread from here

B. Marshmallow GAPPS [6.x.x]

1. Slim GAPPS: Visit Xda thread from here

2. Banks GAPPS 20156-12-22 6.x.x [Dyanmic]: Download from here

3. Open GAPPS: Visit Open GAPPS Site From Here

(Select ARM, Select 6.0 and Select Mini/Micro/Nano/Pico)

Credits: [@dankoman for Slim GAPPS] [dirtyunicorns.com for BANKS GAPPS]

C. Xposed Framework and Installer for Marshmallow [6.x.x]

Visit rovo89's Xda Thread from here (for xposed framework installer, xposed installer apk and xposed framework uninsaller)

Xposed Framework: Choose xposed-v78-sdk23-arm.zip [ (Flash via Custom Recovery)

Xposed Installer 3.0 Alpha4.apk: Choose XposedInstaller_3.0_alpha4.apk (Install as normal apk)

Material Design Xposed Insaller Apk: Visit Xda thread from here (Install as normal apk)

Xposed Framework Uninstaller: Choose xposed-uninstaller-20150831-arm.zip (Flash via Custom Recovery)

Xposed Modules List: Visit Xposed Module Repository Site from here (Install as normal apk)

Credits: [@rovo89 for Xposed Insaller apk, xposed framework installer & xposed framework uninstaller] [@hjmodi for material xposed installer apk]

D. Kernels for Marshmallow [6.x.x]

1. MONARCH kernel: Visit xda thread from here

2. ThunderZap Kernel | Simple Yet Powerful!

(Download ThunderZap Control App from play store for updaing ThunderZap Kernel Update) [Click here for Play Store Free | Click here for Play Store Paid]

a) ThunderZap 5.0 visit xda thread from here

3. Zeus-Kernel v4.5 | Tried | Tested | Trusted: Visit xda thread from here

4. Unknown-Kernel_3.0: Visit xda thread from here

5. Cody Kernel ~ 15||11||2015 ~ REVAMPED: Visit xda thread from here

6. Roar-Kernel-v2.64 by Nazmul Hasan: Dowload from here

7. [KERNEL][MM/LP] ElectraBlue Kernel : Visit xda thread from here