Stock Price allows you to query the current stock price for any symbol that's available through Yahoo's Finance API. It not only shows the current price and company name, but also indicates whether that last price change was positive or negative.
Clone/download this repository's master and double-click the Stock Price.lnbaction. LaunchBar will then prompt you, whether you'd want to install it.
Type sto and Stock Price should then appear. Press the Space key and type in a stock symbol - then simply wait a few seconds. Press the Enter key to open the chosen symbol in your browser (-> finance.yahoo.com).