Uppercase, Lowercse, Swapcase

In Vim, you can use the following motions to modify the case of an entity.

gum - lowercase text operated on by motion
gUm - uppercase text operated on by motion
g~m - switch case operated on by motion
~   - if notildeop is set (default), switch case under cursor
~   - if tildeop is set, switch case of {motion} text

Examples:

guw - lowercase current word
gU$ - uppercase to end of line
g~w - swapcase current word
v$~ - swapcase to end of line (if notildeop is set)
~w  - swapcase of word (if tiildeop is set)