Here are 5 of them.
Number 5: DefaultPlank's Default theme is a nice, minimalist, grey-ish theme.
Number 4: HUDThe HUD theme is darker than the default theme. The glow underneath the applications is more visible, a nice feature.
Download it here.
Number 3: TransparentThe Transparent theme uses a tiny, tiny black space at the bottom of Plank. You can barely see it. Download it here.
Number 2: Glass PillGlass Pill is a blue-ish theme for Plank, which takes up more space than the themes before and looks like, well... a glass pill. Download it here.
Number 1: DarktheonDarktheon is, as the name says, a darker version of the pantheon theme. It gives it a really nice style. The glow underneath the symbols is especially nice to look at. Download it here. (Credit: Colton Allen)
Are there themes we missed that you think should have been in our top five? Leave them in the comments!