Here is a smooth gradient I did the other day utilizing 2 polishes that can give off that mauve-y grandma tone that some people don't care for. I actually like it and I think the gradient fade makes it much more interesting.
The 2 polishes I used are both Wet N Wild Megalasts.
Undercover & Haze of Love
(The one on the right is a mini bottle from a large variety set mom got me.)