Email Client: I'm pretty much all web apps, and would actually like not having evolution or thunderbird installed by default. I think email clients are something to leave up to the users to specifically install
Terminal: Gnome Terminal
IDE: Visual Studio Code. I don't care if it's installed by default, but the ability to install out of the box without a web visit and .deb download would be great.
File manager: I guess I use Nautilus by default, but don't take that as an endorsement
Basic Text Editor: I use vim, but Gedit suffices.
IRC/Messaging Client: Like email, I think this should be left out of a base install these days.
PDF Reader: Evnince it fine, but ePub support in it, or what ever PDF/document viewer is default would be wonderful(bonuse points for mobi too)
Office Suite: Libre Office seems to be the only real option and it's fine
Calendar: Gnome Calendar
Video Player: I used to install VLC day, one, but actually have kept Totem lately
Music Player: I don't think there's any good options, Rhythmbox is still much better than Gnome Music if you're tempted to go all Gnome with the default DE switch
Photo Viewer: EOG is fine, just don't make a big heavy gallery app the default opener even if one is installed by default.