[Galaxy S III General] jinosong:
Notice: The OP has been updated on 2/05/2014. It is updated to reflect the 4.3 platform and has been streamlined with more XPosed modules. The older 4.1.2 post has now been deleted. The OP serves as a representation of our current ongoing discussion of kernels, mods/tweaks and tips on the i9300. It is merely a summary for newcomers to integrate to our discussion.

Most of the forum regulars are very advanced users who know the ins and outs of our phone and how to maximize its performance. I just wanted to share with you some of the most useful mods I've encountered during my brief time on this forum. In my opinion, these mods are not given enough credit for what they can do. Perhaps, some users are not aware of them. Hence, my decision to open a thread to discuss these mods. Feel free to add some of your hidden gems (not the obvious ones).

Kernel

Boeffla Kernel for 4.3

Our go to kernel since 4.1.2. It's not the most feature rich, but it is the most stable and is updated regularly. It includes multiple governors, Boeffla Sound, ZRam and Low Memory Settings. Check it out and gain substantial battery savings over the stock kernel.

Boeffla Kernel

XPosed

II. Xposed Framework

Custom roms for Android have come a long way and Xposed is the next step in customization. It allows users to install modules to customize just about every aspect of your phone. It really minimizes the need for custom roms since it can do everything you need.

Xposed Installer

XPosed Modules

I. App Settings - My favorite app to control the DPI of each individual app. I like setting my phone to around 260-280 so I only set my launcher to that setting while retaining the 320 dpi of the phone itself. Then I customize each app DPI separately.

App Settings

II. AppOpsExposed - Access the secret Android menu to control user information accessed by apps.

AppOpsXposed

III. BootManager - Control which apps are allowed to start up. Some apps simply don't need to start unnecessarily. (ie. Maps, Starbucks, Yelp)

BootManager

IV.Greenify - Sort of like freezing using Titanium Backup, this app finds useless apps that are running in the background and forces hibernation. This will help enable our phones to properly enter deep sleep for better battery life.

Greenify

V. NotifyClean - Control which notifications are allowed to post notifications on the status bar.

NotifyClean

VI. WanamXposed - This is a must for Xposed users. It allows for so much customization. If you own a 4.3 Samsung phone, you absolutely need this.

WanamXposed

VII. XButtonActions - This module will allows users to program their physical keys for certain actions. Remember the long press menu to kill mod? This can do that for you.

XButtonActions

VIII. Disable Clear Defaults Dialog - After setting a default app on TouchWiz this annoying dialog pops up. Disable it with this module.

Disable Clear Defaults Dialog

IX. Free Music Subscription - A certain music subscription app who's name starts with an S (It also rhymes with "modify") has released a free version for tablet users. This module fakes the app into thinking you're using a tablet. I tried it and it works perfectly. Saved $10 a month with this mod. Please don't mention the music app by name here.

Enable Free Music Subscription

Apps

I. Lux

This app essentially controls the backlight automatically for you according to the lighting conditions around you. Handy for saving battery and saving your eyes when you're in bed with the lights off.

Lux

II. Cerberus

Locate your phone when you lose it. Also lets you take a picture, record sound, get call logs, read SMS and so much more. Every Android user needs this.

Cerberus

III. Google Maps 6.14.4

Ever since the new Google Maps was updated, it lost many of it's core features such as offline maps. This is the old APK and resigned so it will never be updated by the PlayStore.

Google Maps 6.14.4

IV. Flash Player on KitKat

Google is trying to phase out Adobe Flash starting with KitKat. This mod will allow it to run those devices. Try installing this with Lucky Patcher found below and watch flash video not allowed on mobile devices. (ie. Hulu, PornHub and ESPN) Be sure to set your browser to desktop mode and disable any ad blockers to watch porn or Hulu.

Flash on KitKat

Lucky Patcher

V. YouTube in HD

This won't speed up your phone but it's worth mentioning. It's does exactly what it says. Watch YouTube in HD.

YouTube in HD

Cosmetic Mods

I. S4 KitKat Statusbar

Gives you the white statusbar found on KitKat. This WiFi icon looks really nice.

S4 KitKat Statusbar

II. DCikonZ Icons

I've become so sick of the S3 icons after looking at them for over a year. Here's an icon pack that's compatible with any third party launcher like Nova, Apex, etc. Icons for XDA, FM Radio, Kindle and YouTube are fantastic.

DCikonZ

III. 4G Icon

Simple mod that turns your H+ icon into a more dynamic 4G icon. I can't remember who made this. Works on both 4.3 and 4.1.2.

4G

IV. Nova Launcher

Most advanced users know and use this launcher but it's worth pointing out that it allows for transparent status bars. Also, enable the shadowing on the status bar and it looks fantastic.

Nova Launcher

V. Google SE Boot Animation and Sounds

This is a very well-known mod that enables the Google SE boot animation instead of the boring Samsung logo. You can enable custom boot animations from here. After enabling, insert bootanimation.zip into data/local or system/media and give permission -rw -r -r. Please note that the bootanimation is not a flashable file. You can also flash the Google SE sounds which will overwrite your Samsung sounds.

Enable Custom Boot Animations

Google SE Animation

Google SE Sounds

Screenshot