Every good bug report at http://bugs.mysql.com matters and may have important findings or useful information inside (even if it is declared as "Not a bug" or "Unsupported"), but based on my experience reports from some people should become a mandatory reading for both MySQL users who care about there servers, and Oracle engineers who process bugs.

Let me name a few of these people, "Top 17" of them based on my totally non-scientific, experience-based approach. You can click on the name to see the list of all bugs reported by this person, started from the recent ones (this may help to understand why I consider their input important).

Shane Bester - 921 bug reports (feature requests excluded, as in all the following cases), based on my non-scientific search. That's really a lot. Shane is famous as a person who can create a test case for any bug (if it is missing) and break any software 9even if it takes weeks of coding and tests running), but he also used to report bugs a lot before Oracle started to demand from employees to use internal bugs database. His one-line crashing bugs were famous. Check Bug #60305, for example (random pick, really) - one prepared statement to crash debug build. His multithreaded test cases written in C are also famous - check Bug #59936 (again, random pick up), even with compile instructions inside. To say nothing about the tools he created and let us all use. Check Gypsy, for example.

Peter Gulutzan - 850 bug reports (even though he had left MySQL team years ago and somewhat disappeared from the ecosystem after that). He designed many MySQL features and surely he spent a lot of time testing them and reporting bugs. Some of bugs he had reported are still not fixed. Check Bug #59004 yourself - I've just checked it on latest and greatest 5.6.10 to see that problem is still repeatable (even though error message changed).

Mark Callaghan - just 214 reports, but Mark never worked for MySQL. Instead he used MySQL a lot in largest and most complex production environments. So, his reports are always about real problems, and usually are a great reading about MySQL internals, with links to other posts, source code, patches, stack traces etc. Check Bug #68481 for one of recent examples. He also continues to use public bugs database, even though Facebook probably still is a customer of Oracle. I appreciate this great example for other Oracle customers.

Philip Stoev worked in MySQL QA for long enough time, and his contribution is still visible. 504 bug reports and a great tool, Random Query Generator, made him famous.

Peter Laursen  with his 401 reports is a great example of a community bug reporter. Not all his reports end up as verified bugs, sometimes he is mistaking and (IMHO) can be even annoying, but his contribution to MySQL quality and documentation over the years was great and important. Check a typical report from him, Bug #68286.

Elena Stepanova also worked in MySQL QA since September, 2008. But she still continues to report bugs to bugs.mysql.com, even after moving on to MariaDB. You can bet your monthly income on her bug reports - they are 100% repeatable and ready to include into MySQL regression tests suite. 206 bug reports, and here is the latest, for 5.6.10: Bug #68472.

Giuseppe Maxia contributed a lot while working in MySQL, before that and after that. 127 bug reports of different categories and famous MySQL Sandbox tool - what else one needs to agree that he is a key member of MySQL Community? Check Bug #68490 for the recent example of how MySQL Sandbox is used to find and verify bugs.

Roel Van de Paar, with his 168 bug reports and ongoing care about Random Query Generator, MySQL test suite and MySQL QA in general (no matter what company he works for), has to be mentioned in any reasonable list of famous bug reporters. Check his recent MTR-related bug report, Bug #68345.

Davi Arnaut mostly fixed (and still fixes) bugs. But even when his bug reports come without a patch ready to apply, they are great. Check one of his recent bug reports, Bug #68501, for a nice way to use new (5.5.28+) InnoDB-related INFORMATION_SCHEMA tables.  

Hartmut Holzgraefe always (for 8+ years) cared about bugs, no matter where he worked and what MySQL related software he had to deal with. Check his latest MySQL Cluster bug report, Bug #67256

Baron Schwartz  reports MySQL bugs at least since 2003. 109 reports in the list. Check one of his latest InnoDB-related reports, Bug #66683

Daniël van Eeden had reported many bugs in different categories, not only for MySQL server. He cares so much that even closes his own reports when the problem is resolved, see Bug #53796.

Surely I have to mention my colleague in yet another company, Alexey Kopytov. This report, Bug #66819, is a mandatory reading for all MySQL DBAs (and something to fix completely finally for Oracle). More than 50 bug reports in total.

Jeremy Cole is famous for his SHOW PROFILE contribution. But even not taking that into account, I had to include him into this list for his current great reports about InnoDB data storage issues and improvements required, like Bug #68023. Check his InnoDB related series of articles also, if you missed it for some reason.

Peter Zaitsev had reported one of the very first public bugs, Bug #16. No surprise that some of his reports, like Bug #51202, are probably forgotten by everybody in Oracle (even when something in 5.6 GA likely allows to solve the problem). He had to create a new company to make things happen, maybe because (among other reasons) of Worklogs and bug reports that hanged around without obvious actions for years.

Domas Mituzas does not report bugs often, but all his reports are great and useful reading - they come from real life use. Check Bug #66921, for example.

Yasufumi Kinoshita contributed many important InnoDB bug reports (and patches). Check Bug #44140, still "Open".

This list surely misses many people whom I'd like to mention. So, to be continued one day...