r - replace a single character

    J - join line below to the current one with one space in between
    gJ - join line below to the current one without space in between

    gwip - reflow paragraph

    g~ - switch case up to motion
    gu - change to lowercase up to motion
    gU - change to uppercase up to motion

    cc - change (replace) entire line
    C - change (replace) to the end of the line
    c$ - change (replace) to the end of the line
    ciw - change (replace) entire word
    cw - change (replace) to the end of the word

    s - delete character and substitute text
    S - delete line and substitute text (same as cc)

    xp - transpose two letters (delete and paste)

    u - undo
    U - restore (undo) last changed line
    Ctrl + r - redo

    . - repeat last command