3 for me ;)

I'd pick number 4, but definitely not 1 or 2. They wouldn't hold up under single color conditions.

Do you need a logo?

Uhh, I'm asking myself the same question as I'm working on mine right now :P

It would be great to have some background info about the logo

#3.

3 and I'll tell you why...

The first two dont visually read as a "v" and an "n" – just an stylized "n" really.

As for the last two, I opt for #3 over #4 because black is usually the default space where the color accents something special. In this case, "n" is apparent but the "v" is only understood when called out by a vibrant color.

Is very hard with no background information...you should give people a bit of context, otherwise you'll just get intuitive judgments based on aesthetic with no contextual meaning.

An "N" for a vet business is quite different from an "N" for the new Netflix logo.

Maybe you could also think about playing with negative space? Don't really know how to explain it so I made very quick example...

http://d.pr/i/1kssd

Cool ideas. I really like 4.

2.

Feels more 3 dimensional to me, a couple of gradient tweaks would make this concept super strong imo.

3 standing out more for me!

I read the first 2 as just N, and the second 2 as just V.

Not getting an NV from that at all soz :(

3rd is the best!

3 or 4 :)

Thanks to all for your comments!

As lot of people has chosen the third one (and I also prefer this) I will use #3. But you can keep giving me your opinion.

3

If it is your personal thing (which I guess it is probably judging from your name), I prefer 3, but only slightly. I think 1 or 2 can definitely work if the surrounding material is done right.