Pens!
I love investing in good writing instruments. Here is the current line up (with a new addition):
Apple pencil for notes I need to keep (meeting notes, important concepts for my app development, ideas for new blog posts)
Mechanical pencil for sketching disposable charts, diagrams, concepts that either need partial creative erasing and/or a ruler (read the review of my trusted Lamy 2000 mechanical pencil here)
And now: a nice roller pen for other “disposable” notes.
Since I started my career at McKinsey back in the 1990s I have been using pencils for everything. Back in the day, all charts and slides were sketched by hand before being produced by a graphics designer who understands PowerPoint (or Solo before that). But, pencils leads break easily when writing enthusiastically and have low contrast, hence the addition of the pen.
The Lamy 2000 roller pairs nicely with my pencil. The design is almost identical to the classic fountain pain, but with less staining (I am left handed), and the need to get that writing angle perfectly right. I think a roller is better for short notes than a proper fountain pen. The Lamy has a perfect balance (wit the cap placed on the back), and somehow the plastic that is used in the pen gives it a really nice brushed feel, and a perfect weight. Only drawback, those two tiny grips that were part of the original design and produce that satisfying click when the cap is closed.