APK Editor is a powerful tool that can edit/hack apk files to do lots of things for fun.
It can help us to do things like string localization, background image replacement, layout re-architecting, and even ad eliminating, permission removing, etc. What it can do depends on how you use it. However, to use it well, we need a little bit professional skills. Don't be afraid, some examples are given in the help page.
(Note: Manifest editing is not supported in free version)

From version APK Editor 1.9.0:
Variant
Arch
Version
DPI
(Android 3.1+)
Latest: 1.6.10 on September 30, 2016
(Android 3.2+)
Latest: 1.8.17 on October 3, 2017
All versions
APK Editor 1.9.0
September 30, 2018

Version:1.9.0

Uploaded:September 30, 2018 at 7:56PM UTC

File size:6.67 MB

Downloads:101,556

APK Editor 1.8.20
November 8, 2017

Version:1.8.20

Uploaded:November 8, 2017 at 11:25PM UTC

File size:9.52 MB

Downloads:24,185

APK Editor 1.8.17
October 3, 2017

Version:1.8.17

Uploaded:October 3, 2017 at 6:39PM UTC

File size:9.48 MB

Downloads:3,823

APK Editor 1.8.15
September 7, 2017

Version:1.8.15

Uploaded:September 7, 2017 at 9:02PM UTC

File size:9.26 MB

Downloads:23,493

APK Editor 1.8.10
August 7, 2017

Version:1.8.10

Uploaded:August 7, 2017 at 7:40PM UTC

File size:9.11 MB

Downloads:3,434

APK Editor 1.8.8
June 14, 2017

Version:1.8.8

Uploaded:June 14, 2017 at 10:50PM UTC

File size:9.08 MB

Downloads:5,845

APK Editor 1.8.7
April 4, 2017

Version:1.8.7

Uploaded:April 4, 2017 at 4:47AM UTC

File size:9.13 MB

Downloads:6,527

APK Editor 1.8.1
February 19, 2017

Version:1.8.1

Uploaded:February 19, 2017 at 7:05PM UTC

File size:9.6 MB

Downloads:16,631

APK Editor 1.6.10
September 30, 2016

Version:1.6.10

Uploaded:September 30, 2016 at 6:36PM UTC

File size:6.03 MB

Downloads:423,881