Most option strategies that market players incorporate into their trading plans involve option contracts whose strike price is close to the trading price of the underlying. People use these contracts to magnify gains and leverage their assets.
But there may be times when you want to get long stock as much as possible without worrying about time decay. By using deep in the money stock options, you can emulate stock movements with less capital at risk. Take a look this option chain of Google (GOOG):
We've broadened out the strike prices so you can see all the options available. The two values listed are delta (the change in the option price versus the change in the underlying) and extrinsic (premium left on the option). You can see that as options get further in the money, the delta increases and the intrinsic decreases. If you get in far enough, you can use a deep in the money option to substitue for stock.
Take the Oct 250 cals. There is only 1.30 of premium left on the option, or 1% of the overall option's value. The since there is almost all intrinsic value, it will mirror the movement of the stock. The 250's have .97 delta, which means it will move $97 for every 1$ move in the stock. This is the equivalent of owning 97 shares.
The upside to this is that you can use this to leverage your assets. If you were to buy 100 shares of google in a non-margined account, you would need $39,000 available. That's a tremendous amount of capital to tie up in one trade. But to get nearly the same amount of exposure, you can buy that 250 call for a cost of 14,170. You can calculate the total leverage like this:
38220 (98 delta at stock cost) / 14170
So you are essentially gaining exposure in GOOG without putting up all the necessary capital.
There are downsides to this. The options market does not have tight spreads compared to the trading in the underlying, so there would be some slippage. And gaining that sort of leverage can be dangerous if you don't know what you're doing. But if you wanted that sort of exposure in the first place without tying up all of your capital, then deep in the money option strategies are a valuable tool.