Number 16 of 20: improved watchpoints
go to the Solaris 10 top 11-20 list for more
Eric Schrock has an overview of watchpoints as well as a discussion of the cool improvements he's made to watchpoints in Solaris 10. Watchpoints have, in the past, been a bit dodgy -- they were only vaguely compatible with C++, multi-threaded code, and x86 stacks. Now they're way more robust and much faster.