Are there any MySQL Benchmarking tools?
Benchmarking or Tuning tool?

IMHO, there's no tool that will be specific to the latter unless you have a super generic usage. You need to identify your usage pattern and tune your database hosts to accommodate. If you're write-heavy, you will have a different configuration than a read-heavy scenario. Bottom line, your tuning follows your applications usage.

For benchmarking, I use Sysbench. Here's an example from my blog.

Added:
Here's my beef with config tools: With the changes in versions 4.x vs 5.x vs 5.5.x there are a lot of tweaks that don't jive between them. So you really need a savvy DBA to evaluate what's going on for each host. Load, storage, traffic, application specific requirements, there's a lot that can go into an optimal configuration. A tool may get you part of the way, but may leave out something or include something that may cause a failure. From buffers to flushing to plugins to threading, a config tool may provide you with false confidence that you are implementing the correct config.