There is no perfect cleaner/optimization tool. A combination of many such tools from different manufacturers can achieve efficient result.
From freeware segment, Ccleaner is most trusted and good enough Registry cleaner and optimizer. It is one of the best as a Trash cleaner.
From the paid segment, WinXP Manager offers good optimizing tools. It's registry cleaner cleans left over snall registry entries too. A combination of this and PC Tools Registry Cleaner is perfect solution.