ggrepel remove line around labels

You can omit the label boxes using the geom_text_repel geom.

library(ggplot2)
library(ggrepel)
g <- ggplot(mtcars, aes(wt, mpg, color = wt)) +
  geom_point(color = 'red') +
  theme_classic(base_size = 16)

g + geom_label_repel(aes(label = rownames(mtcars)), fill = "white")

g + geom_text_repel(aes(label = rownames(mtcars)))

Also, according to the help page:

Currently geom_label_repel ... is considerably slower than geom_text_repel.

As eipi10 noted in the comment, set label.size=NA:

library(ggplot2)
library(ggrepel)
ggplot(mtcars, aes(wt, mpg, color = wt)) +
  geom_point(color = 'red') +
  geom_label_repel(aes(label = rownames(mtcars)), label.size = NA, fill = "white") +
  theme_classic(base_size = 16)