* TSX ends down 17.36 points, or 0.11 percent, at 16,165.27
* Six of the TSX's 10 main groups move lower
TORONTO, Dec 22 (Reuters) - Canada's benchmark stock index slipped on Friday but notched its sharpest weekly gain in almost three months, as big banks and some miners pulled back.
* The Toronto Stock Exchange's S&P/TSX composite index .GSPTSE ended down 17.36 points, or 0.11 percent, at 16,165.27.
* It gained 0.8 percent over the course of the week, its sharpest weekly gain since last November, after notching a fresh all-time high on Monday.
* Six of the index's 10 main sectors closed lower, although most of the moves were marginal in lower volumes ahead of the Christmas holiday break, which closes Canadian markets next Monday and Tuesday.
* The energy group retreated 0.1 percent, while the financials group slipped 0.3 percent as data showed economic growth stalled in October. Among the most influential decliners on the index was First Majestic Silver Corp FR.TO , which fell 9.3 percent to C$8.82 after Bank of Montreal analysts cut the stock to "underperform" and lowered its price target.
* First Quantum Minerals Ltd FM.TO declined 2.8 percent to C$17.12, while the overall materials group, which includes precious and base metal miners and fertilizer companies, added 0.4 percent.