I would add
the power of Konqueror.
File Manager, FTP/SFTP tool, action menus, image viewer, webbrowser, and
more.
I second that one (and of course support the other arguments). Konqueror as a
file browser is THE reason I never wanted to go away from KDE 3.
KDE 4 did add some of these features in Dolphin, but every time I open
Konqueror I just feel "at home".
I do also like and often use xfce4 but the versatility of konqueror in
TDE seems unmatched anywhere else.
Debian Jessie actually removed gftp (which was anyway comparatively
crippled)
Other one is kdiff3.. there is meld in gtk but (imo) it's a poorer
substitute.
D