Never saw anyone try this before and I've seen just about everything including javascript in user agents trying to redirect to malware sites.
188.190.124.66
<br><center><h1>Pilferer</h1></center><br><center><h2><a href="http://example.com/">[Toolly Robot 0.1]</a></h2></center>
FYI, I replaced the domain with example.com because this one is not safe to surf and I'm not promoting it here just in case someone isn't careful and got hammered by accident.
Beware as user agent strings, referrers and even the requested pages are a potential vulnerability, just like cross-site scripting, which could be used to attack to your MySQL queries and reports if not properly filtered.
Best case, as in the above example, the code just messes up the report and displays the user agent in a big font in the middle of the screen with a link to their site.
Worst case, it contains a javascript redirect and or attempts at MySQL attacks.
People tend to filter malicious input from being passed to their web pages but ignore the fact that this data can also logged in it's raw form and then processed later by server stats programs that don't always filter that data properly to protect webmasters from simplistic browser or SQL attacks. Once I noticed this stuff happening I stopped all server side log analysis programs as I can't be sure they are secure and won't let something through that puts my server or browser at risk.
