IMHO, Topaz 'Clarity', and 'Detail' are must-haves for bringing your images to life, and if one requires such things, 'Remask' is pretty good.
'Denoise' is also one of the better denoising programs, alongside NeatImage and Noise Ninja which are also good but more expensive especially over time.
I am in 100% agreement with Bart about his most frequently used plugins, I use them also all the time. However, it seems that when using both, Detail and Clarity on the same image, sometimes they fight each other, so now I choose one or the other, but not both. Maybe there is a method to use effectively both in the same image, but I find that either one improves the apparent contrast and pop.
Also, in the last year I have started to use the artistic filter Impression on some images. This plugin contains over 600 effects, ranging from B&W pencil and charcoal sketches to oil and watercolor treatments. I use mainly their oil and impasto filters, sometimes to a quite interesting and striking effect. For sure, this is not everyone's cup of tea, but I find that in some cases the abstract and blurred interpretation may result in a more appealing picture than the original sharp photographic image.
There is another similar plugin, called Simplify which overlaps somewhat with Impression, but Impression is a more substantial and feature rich program.
Both plugins can be found here:
Topaz Labs StoreAs an example, attached is one of my Havana images, followed by three different Topaz Impression renditions.