One of the interesting ones we encountered was in the JDBC driver of our chosen database at the time. Under load, the application core dumped. Mind you this is java, running a native jdbc driver, no JNI in sight. It took some gdb stepping to figure out that under load, the JIT compiler got a little aggressive and inlined a little more code than there was room in the JIT buffer - result? a completely random core dump. Once I did find it, it was a simple matter of increasing JIT buffer size and adding more heap and ram. Tracing assembler generated from byte code generated from java was just part of the issue, the fact that the code itself had nothing to do with the issue is what made it interesting as the buffer size is set in a completely different area by the jvm. Fun times.