Gmail Short Cut

 C: Compose new message.
    Shift + C: Open new window to compose new message.
    Slash (/): Switch focus to search box.
    K: Switch focus to the next most recent email. Enter or "O" opens focused email.
    J: Switch focus to the next oldest email.
    N: Switch focus to the next message in the "conversation." Enter or "O" expands/collapses messages.
    P: Switch focus to the previous message.
    U: Takes you back to the inbox and checks for new mail.
    Y: Various actions depending on current view:
    Has no effect in "Sent" and "All Mail" views.
        Inbox: Archive email or message.
        Starred: Unstar email or message.
        Spam: Unmark as spam and move back to "Inbox."
        Trash: Move back to "Inbox."
        Any label: Remove the label.
    X: "Check" an email. Various actions can be performed against all checked emails.
    S: "Star" an email. Identical to the more familiar term, "flagging."
    R: Reply to the email.
    A: Reply to all recipients of the email.
    F: Forward an email.
    Shift + R: Reply to the email in a new window.
    Shift + A: Reply to all recipients of the email in a new window.
    Shift + F: Forward an email in a new window.
    Shift + 1 (!): Mark an email as spam and remove it from the inbox.
    G then I: Switch to "Inbox" view.
    G then S: Switch to "Starred" view.
    G then A: Switch to "All Mail" view.
    G then C: Switch to "Contacts" view.
    G then S: Switch to "Drafts" view.

From - YTPCC