The FTSE 100 keeps on motoring on and on. This week it touched new record highs above 10,700 points, taking total gains over the last 12 months to 22%.

Yet despite these stunning gains, many top shares continue to change hands at bargain-basement prices. GSK (LSE:GSK) is one company that trades at an enormous discount to its market peers, while Fresnillo (LSE:FRES) still looks cheap relative to expected profits.

JD Sports Fashion (LSE:JD.) is the final FTSE share I think could be too cheap to ignore. Read on to find out why each of these shares deserves serious consideration.

GSK

GSK’s share price has risen 57% over the last 12 months. However, years of underperformance mean it continues to trade at a chunky discount to the broader global pharmaceuticals sector.

At £22.61, its forward price-to-earnings (P/E) ratio is 14.1 times. That’s far below the industry average of roughly 21.

GSK still faces challenges in the field of US vaccine sales. Though this may remain a problem, strength across the rest of the portfolio — and the shift towards higher-margin products — means the outlook here is a bright one.

The company’s prior price lag reflected a weaker drugs pipeline compared to its rivals. But the FTSE firm has invested heavily in R&D to transform its fortunes, and is targeting sales of £40bn by 2031 (last year’s revenues were £32.7bn).

Fresnillo

Surging precious metal prices have thrust Fresnillo’s share price 399% higher over the past year. But with a forward price-to-earnings growth (PEG) ratio of 0.2 for 2026, the silver miner still offers excellent value at £39.10 per share.

Any reading below 1 implies a share trading below value.

Fresnillo’s shares have hit turbulence more recently, reflecting a falling silver price as investors have booked profits. Further volatility could be in store, especially if economic conditions worsen and demand for industrial silver darkens.

On balance, though, I think there’s plenty of scope for the dual-role metal to rise again. Falling interest rates, a slipping US dollar, and rising geopolitical uncertainty should support strong investment interest. I’m also expecting solid industrial offtake given the metal’s important role in growth industries like renewable energy and information technology.

JD Sports Fashion

JD Sports faces the prospect of weak consumer spending enduring in key markets like the US. Reflecting this, the company’s shares have dropped 6% over the last year to 79.3p today.

But could investors be overly gloomy about the FTSE 100 retailer’s prospects? Given JD Sports’ rock-bottom valuation, I think they may be — today its shares trade on a forward P/E of just 6.7 times.

Though the business faces severe challenges, latest financials showed some signs of recovery. Sales over the Christmas period came in better than forecast, thanks in part to more positive performance in North America. As interest rates fall and consumer spending improves, this trend could continue.

Over the long term, I’m expecting JD Sports’ share price to rebound as growth in the ‘athleisure’ market picks up.