I ran out and picked about a 1/2 cup of mallow (cheese weed) fruits as our heat wave was making everything mature rapidly. The pickling liquid was white wine vinegar, a touch of course ground mustard, bit of salt and sugar - warmed and poured over in the little jar. I had previously only nibbled them raw as a kid. After sitting for a few days, a spoonful in my tuna salad was nice instead of pickle relish.
Plant info http://www.ipm.ucdavis.edu/PMG/WEEDS/little_mallow.html