The Basingstoke-based firm fell as much as 12 per cent as some analysts voiced fears that Game could face tougher competition in a more challenging environment for retailers.
Game - buoyed by the launch of Nintendo's Wii Fit and Grand Theft Auto IV - has so far evaded the misery hitting home elsewhere on the high street. Its shares have risen 62pc in the past 12 months.
But Investec's David Jeary said "Our fundamental view remains that Game is approaching the top of the current cycle and that competitive and pricing pressures are increasing."
The growing rivalry was shown earlier this week as HMV reported increased profits after shifting the focus of the business towards games sales.
But Game nonetheless posted a 28.1pc rise in UK like-for-like sales in the 22 weeks to June 28, with other big sellers for the company including Mario Kart and Metal Gear Solid 4.
Although the firm said the quality of the games released during the first half of 2008 was "unprecedented", it remained confident over Christmas trading.
Margins
Chairman Peter Lewis said the group "recognised the challenges of the wider economic environment", but has improved its margins and expects profits for the six months to July 31 to be no less than £33 million.
The company, which bought rival Gamestation last year, said it was continuing with its roll-out of new stores despite the difficult climate and investing £42 million on capital expenditure.
The group currently has 668 stores in the UK and Ireland, but most of the 60 stores to be opened by the end of the year will be overseas as part of its international growth strategy.
Meanwhile Game has also drafted in Dennis Woodside as a non-executive director. Mr Woodside is the managing director of search engine giant Google in the UK, Ireland and Benelux countries and the firm hopes to benefit from his expertise in online retailing.
Other analysts took a more upbeat view of prospects despite today's sell-off. Nick Bubb of Pali International said: "This cycle is completely different than any other cycle, given the much broader and deeper range of formats and consumers involved and the games market boom is likely to continue."
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