F5 BIG-IP
The BIG-IPs are a widely known load balancer platform. From early on, they've had one of the most complete implementations of performance metrics in the industry. There are a wide variety of metrics available through SNMP, and the basic, most important ones are listed here.The BIG-IP MIB file can be found by logging into the command line interface (via SSH) and looking at the following location:
/usr/contrib/f5/mibs/
Depending on the version of code you have, there may be one or more files in there. The most important one is LOAD-BAL-SYSTEM-MIB.txt.
To view all the metrics available via SNMP, just load that MIB file into your favorite MIB browser (mine is net-snmp) and browse away.
With the 4.x code base, F5 changed around a few of their metrics and where they are reported via SNMP. The versions that I've tested (up to 4.2) still work with the older 3.x OIDs, but they've been marked as deprecated, so in future versions the new OIDs may be the only ones that work.