This article has been adapted from  Fool U.K. , our sister site across the pond.

I finally persuaded my wife to open her first stocks and shares ISA last week, which I have offered to manage for her. This has got me thinking about which shares I would buy if I had a stash of cash to invest today. Here are a few suggestions.

AstraZeneca
I have written before about Big Pharma. I am sticking with the view that, with the forthcoming boom in biologics and the expansion into emerging markets, pharma stocks are seriously underrated at the moment.

This view is shared by fund management great and income specialist Neil Woodford, whose funds have major holdings in both AstraZeneca (NYSE: AZN) and GlaxoSmithKline.

The recent rise in these shares suggests that the market is starting to agree with this viewpoint. With life expectancies increasing and health-care expenditure continuing to rise across the globe, the demand drivers remain strong for the pharmaceutical industry.

However, AstraZeneca has had a difficult time recently, having been hit by a flurry of patent expiries and a disappointing pipeline. This has taken its toll on the share price, and the drugmaker currently stands at a P/E ratio of 7.6.

I think this is cheap as chips, because I expect AstraZeneca to continue to throw itself into innovating. The company has recently placed a greater emphasis on biologics, and I expect this strategic shift to drive future long-term growth for this company.

Shell
The commodities boom is taking a breather at the moment, and commodities stocks have recently fallen back. But in the longer term, I feel the boom will roll on, as demand for commodities continues to rise and supply tightens.

So I see the current dip as a buying opportunity for commodity stocks such as oil leviathan Royal Dutch Shell (NYSE: RDS-B).

Last year, given the choice between investing in Shell or BP, I plumped for BP, thinking of it as a contrarian play after the Macondo oil spill.

With hindsight, this was clearly a mistake, as BP's recovery was cut short by the Rosneft/TNK-BP fiasco, while Shell has steered clear of trouble and seems to be serenely growing its profits as the oil price rises. A fellow Fool has also noted that it is an increasingly big player in natural gas.

It must be particularly galling for BP to see Shell chief executive Peter Voser enter into talks with Rosneft about the Arctic oil fields which have slipped, tantalizingly, from BP's grasp.

Aviva
Blue chips are out of fashion. Financials are out of fashion. So a blue chip financial would seem like the perfect contrarian play.

Insurance companies in particular seem to have been pulled down with the banks, even though the insurers are in much better financial health.

There are a bevy of insurers which look cheap at the moment. Along with Aviva (NYSE: AV), there is Legal & General, Amlin, and RSA Insurance. I think reasonable cases could be made for investing in any of these at the moment.

But I would go with Aviva as it is the biggest, the cheapest, and has a tempting dividend yield. After rising steadily through the past 12 months, the share price has fallen back from its 2011 high, leaving the company on a P/E ratio below 10. If you haven't bought in to Aviva yet, this could be a good moment to do so.

Dialight
After choosing three blue-chip high yielders, I thought I'd round off with a small-cap growth stock. The one I have chosen is Dialight, which trades on the LSE. This company is currently one of the top five holdings in U.K. growth guru Mark Slater's outperforming MFM Slater Growth fund.

Dialight is one of the leading companies in the field of LEDs (light-emitting diodes). LEDs are a form of lighting, their key advantage being that they reduce energy costs by up to 90% compared to standard lighting.

With rising energy prices and an increasing drive to lower electricity usage, LEDs have massive potential for growth. LEDs are increasingly used in traffic lights, industrial lighting, and obstruction lighting. Dialight is a major player in all three areas, and it also has a growing business in smart metering. High-quality and well-patented research gives the company an edge in these niches.

Group operating profit in 2010 more than doubled to 11.2 million pounds. With such a rapid rate of growth, the share price has also more than doubled in a year, and the small cap is on a forward P/E ratio of 26.

So Dialight is not cheap, and it might make sense to wait for a dip before buying in. But I think the shares have plenty of momentum, and, long term, I see this as a small company that could get a lot bigger.

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