Here is a small list of messenger shortcuts to speed up your chatting and the whole WLM experience. Also these shortcuts speed up all the other WLM feature access times. So learn them and have a go at it. Do chatting much faster… 
Ctrl + B = Text Bold;
Ctrl + T = Text Italic;
Ctrl + U = Text Underline;
Ctrl + Q = Opens the Sounds in Messenger Plus;
Ctrl + E = Opens Emoticons;
Ctrl + R = Table Opens Colors Messenger plus;
Ctrl +8 – Ctrl +2 = Log messages from that conversation (numeric keypad);
Crtl + F = Find text (unless you messenger plus);
Ctrl + space = Block Messenger (unless you messenger plus);
Ctrl + S = Search the underlined word on live.com;
Alt-F4 = Close the conversation;
F1 = Help Windows live messenger;
F2 = Register a voicemail;
F10 = Show bar formatting.
Source: msntribre
