Just scored this beast of a grinder - what should I tackle first?

Nice pickup! That's a solid workhorse. First thing - check the wheel guard alignment and make sure you've got a quality diamond blade if you're cutting masonry. I'd start with something simple like cleaning up some old rebar or cutting pavers. Don't go straight for demo work until you get the feel of it.

Ooh shiny! I use mine mostly for cutting ductwork and cleaning up HVAC brackets. Pro tip - get a wire cup brush attachment for cleaning rust off fittings. Makes my life way easier when installing units. Also, wear a mask - that metal dust gets everywhere!

That thing looks mean! I'd test it on some concrete edges - see how it handles feathering. Just did a patio last week where mine saved hours on cleanup. Watch the kickback on hard materials though. Almost lost a thumb once when it caught on rebar.

Before you even plug it in - safety glasses, gloves, and hearing protection! I've seen too many sparkies come into my jobs with metal shavings in their eyes. Also, keep a fire extinguisher nearby if you're grinding indoors. Drywall dust + sparks = bad news.