I've been on Stack Overflow since January 2009 and participated on Meta since its founding as Meta.StackOverflow.
I have accounts on a number of other Stack Exchange sites so I think I have a good idea of what's going on across the network.
763 Encouraging people to explain downvotes Jun 28 '09
170 Is it OK to leave “What have you tried?” comments? Feb 21 '12
105 What do icons on the tags mean? Nov 18 '09
100 Can we have a moderator only “flag for community team/developer attention” link on posts? Feb 18 '12
98 Add a strike-through to the editing interface Jul 26 '09
94 Reputation for comments? Jun 28 '09
84 Winter Bash closing remarks - ideas for next year Jan 4 '15
79 Can we get some more review queues - questions with delete votes, recently closed etc.? Sep 24 '12
73 Why is upvoting being recommended here? Dec 31 '12