I'd be interested to hear what you are using.
Obviously the web browsers are a big requirement.
...but I've had trouble with the defaults for almost everything I've tried: xterm, libreoffice, browsers. Under KDE the menus are too small by default. Under non-Gnome-or-KDE window managers or desktop environments almost everything is rendered too small.
The chances are that I can't just install an application with `apt-get` and have it do something sensible by default without a lot of fiddling and customisation.