What is your favourite image viewer?

For years gThumb was my preferred image viewer/cataloguer, although I used qiv for imdividual images in e.g. Midnight Commander and still do.

Then along came Gnome 3 and reduced it to trash, along with everything else that got Gnome 3'd.

So I struggled through several others before settling on Nomacs. It does a few things well and uniquely, but is very quirky and, despite a wealth of features that i never use, lacks such simple essentials as bookmarks.

What are others using?