Linux – using sudo on GUI applications

When I was using kubuntu, I could always open X applications with sudo, sudo kate for example. Now that I've switched to arch that doesn't work. I know I've always been told to use kdesu, but what setting is there in kubuntu that lets me use sudo on X apps that prevents me from doing it on arch?

Edit:
Sorry, I did myself what I hate so much >_<

This is what I'm trying to do:

[falmarri@falmarri-z-arch Downloads]$ sudo kate
Password: 
No protocol specified
kate: cannot connect to X server :0.0

Note this is just a regular terminal session using konsole, I'm not using SSH

/etc/sudoers:

## sudoers file.
##
## This file MUST be edited with the 'visudo' command as root.
## Failure to use 'visudo' may result in syntax or file permission errors
## that prevent sudo from running.
##
## See the sudoers man page for the details on how to write a sudoers file.
##

##
## Host alias specification
##
## Groups of machines. These may include host names (optionally with wildcards),
## IP addresses, network numbers or netgroups.
# Host_Alias    WEBSERVERS = www1, www2, www3

##
## User alias specification
##
## Groups of users.  These may consist of user names, uids, Unix groups,
## or netgroups.
# User_Alias    ADMINS = millert, dowdy, mikef

##
## Cmnd alias specification
##
## Groups of commands.  Often used to group related commands together.                                                               
# Cmnd_Alias    PROCESSES = /usr/bin/nice, /bin/kill, /usr/bin/renice, \                                                             
#                           /usr/bin/pkill, /usr/bin/top                                                                             

##                                                                                                                                   
## Defaults specification                                                                                                            
##                                                                                                                                   
## You may wish to keep some of the following environment variables                                                                  
## when running commands via sudo.                                                                                                   
##                                                                                                                                   
## Locale settings                                                                                                                   
# Defaults env_keep += "LANG LANGUAGE LINGUAS LC_* _XKB_CHARSET"                                                                     
##                                                                                                                                   
## Run X applications through sudo; HOME is used to find the                                                                         
## .Xauthority file.  Note that other programs use HOME to find                                                                      
## configuration files and this may lead to privilege escalation!                                                                    
 Defaults env_keep += "HOME"                                                                                                         
##                                                                                                                                   
## X11 resource path settings                                                                                                        
 Defaults env_keep += "XAPPLRESDIR XFILESEARCHPATH XUSERFILESEARCHPATH"                                                              
##                                                                                                                                   
## Desktop path settings                                                                                                             
 Defaults env_keep += "QTDIR KDEDIR"                                                                                                 
##                                                                                                                                   
## Allow sudo-run commands to inherit the callers' ConsoleKit session
# Defaults env_keep += "XDG_SESSION_COOKIE"
##
## Uncomment to enable special input methods.  Care should be taken as
## this may allow users to subvert the command being run via sudo.
 Defaults env_keep += "XMODIFIERS GTK_IM_MODULE QT_IM_MODULE QT_IM_SWITCHER"
##
## Uncomment to enable logging of a command's output, except for
## sudoreplay and reboot.  Use sudoreplay to play back logged sessions.
# Defaults log_output
# Defaults!/usr/bin/sudoreplay !log_output
# Defaults!/usr/local/bin/sudoreplay !log_output
# Defaults!/sbin/reboot !log_output

##
## Runas alias specification
##


Defaults:falmarri timestamp_timeout=10

##
## User privilege specification
##
root ALL=(ALL) ALL

## Uncomment to allow members of group wheel to execute any command
%wheel ALL=(ALL) ALL

## Same thing without a password
# %wheel ALL=(ALL) NOPASSWD: ALL

## Uncomment to allow members of group sudo to execute any command
# %sudo ALL=(ALL) ALL

## Uncomment to allow any user to run sudo if they know the password
## of the user they are running the command as (root by default).
# Defaults targetpw  # Ask for the password of the target user
# ALL ALL=(ALL) ALL  # WARNING: only use this together with 'Defaults targetpw'

## Read drop-in files from /etc/sudoers.d
## (the '#' here does not indicate a comment)
#includedir /etc/sudoers.d