<sup>*By Alone-zee's request i trasfer here my comments made in response to identical sub-question [in another thread](https://russian.stackexchange.com/a/16185/7674)*</sup>

**ну и** is an emphatic compound interjection in exclamations expressing negative emotions or attitude, it functions as the English **what a...; such a...; so...** but only in a negative context, e.g. 

> **Ну и** погодка сегодня! - **What a** terrible weather we have today! 
> 
> **Ну и** дурак **же** ты!/**Ну** ты **и** дурак! - You're **such a** fool! 
> 
> **Ну** ты **и** загнул!/**Ну** **и** загнул **же** ты! - You're **so** exaggerating! 
> 
> [**Ну и** видок у тебя,
> Шарапов!](https://www.youtube.com/watch?v=ogIxmP5hwA4) - You have **such
> a** terrible look, Sharapov!

`- Could it be that this "и" is a particle for emphasis that often precedes a verb?`

**ну и** goes not only with verbs and rather to a lesser extent with verbs, and it doesn't follow some previous statement for confirmation or reinforcement, it is perfectly autonomous and self-contained.

Check these examples of usage with a verb: 

**`1.`** **Ну** ты **и** пишешь! <sup>*(a comment about quality of handwriting)*</sup> - You have **such an** awful handwriting! <sup>*(characters are either too small, illegible, ugly, don't meet some arbitrary requirements or something else etc)*</sup> 

VERSUS 

in a dialogue: 

**`2.`**   
-Зачем я это пишу? - Why am i even writing this?  
-Тебе сказали писать?  - Have you been told to write this?  
-Да. - Yes.  
-Ну / Вот / Ну вот ты и пишешь. - So that's why you're writing.

Note that in the second example the phrase doesn't end with exclamation mark, it would be inappropriate here because it's not an exclamation.