I used to recommend snagit, they have a mac version but they've turned to the darkside and its now subscription based. I use an older version that I bought from them - still works. Not sure if its going to be compatible with Tahoe, but I hope so
I also like CMD+Shift+4 followed by a press of the space bar. Captures a full window complete with the little drop shadow. It's very slick for some uses.
Very cool. It's always striking to me how many Mac features are basically easter eggs because they're so hidden.
MacOSXHints.com was amazing for surfacing this kind of thing.