I reviewed a paper for PLOS One in 2014 and got a nice acknowledgment, but I also reviewed a paper for the same journal in 2015. Here’s the acknowledgment for that contribution. They’re still having a bit of trouble with alphabetization (Steve Simon should be the last “Simon” on the list, but it’s not). Still, it’s nice to have a public record of my small contribution.
(2016) PLOS ONE 2015 Reviewer Thank You. PLoS ONE 11(2): e0150341. doi:10.1371/journal.pone.0150341. Available at http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150341.