When management believes that its company's shares are trading at a discount and ample cash is overflowing in the business's coffers, one of the best ways to create value for investors is through share buybacks. In addition to paying investors who no longer wish to own the shares in question, buybacks allow the company to reward loyal investors by increasing their stake in the company. While some companies issue small buybacks to appease investors, some take it to a whole new level.

 CompanyBuyback Amount at Current PricePercent of Total Shares to be Bought
Sirius XM Radio  $2.2 billion  11.3%
Comcast   $10 billion  5.7%-11.4%
AT&T   $10.5 billion  5.7%
Hertz Global Holdings   $1 billion  8.4%

Source: Company filings.

Talk about getting Sirius
One of the biggest buyback stories in the news is Sirius XM Radio (NASDAQ:SIRI). After announcing in October that it would be repurchasing $2 billion worth of its shares, on top of its previously authorized $2 billion buyback, shares of the satellite radio provider fell 18%, from $3.91 to $3.20. At first glance, this may seem terrible. But for the long-term investor, the news is anything but.

With about $2.2 billion worth of shares that can still be repurchased under its current plans, the company can buy back an extra 57.1 million shares. That's a total of 687.5 million shares at current prices versus the 630.4 million shares the company could have bought at year-end. To put this differently, the share buyback from current levels would serve to reduce the company's shares outstanding by a whopping 11%, which should make an investment in the company look quite appealing.

Comcast is ramping things up
In an interview with Bloomberg on March 31, Michael Angelakis, the CFO of Comcast (NASDAQ:CMCSA), announced that the company is considering increasing its share-buyback program for 2014 by $2.5 billion. The increase depends on whether its deal to buy Time Warner Cable is approved by regulators. This comes on top of the company's commitment to repurchase $3 billion for the year and would increase Comcast's current buyback authorization from $7.5 billion to $10 billion.

At the company's closing share price on March 31, a share buyback of this size would reduce Comcast's shares outstanding by nearly 8%. However, after the company merges with Time Warner, the impact on shares will only be about 6%. That's unless management decides to follow through with an extra $10 billion in share repurchases it alluded to in its announcement to acquire its smaller rival. At that level, investors would increase their ownership in the combined company by up to 11%. No matter how you stack it, that's some serious repurchasing.

Talkin' 'bout telecom...
Sticking with telecommunications companies, we arrive at AT&T (NYSE:T). On March 31, the company said that it is planning to repurchase up to an extra 300 million shares. This comes on top of the 775 million shares the business has bought back since 2012, and is currently valued at around $10.5 billion.

With AT&T's market cap of $183 billion, the deal amounts to only 6% of its shares outstanding. But -- perhaps more than any of the companies profiled here -- it seems to be on the right track. Using 2013's earnings per share of $3.39, shares of the company are trading at a modest 10 times earnings. This is a significant discount to the 20 times Comcast is going for and a fraction of Sirius' 53-times-earnings multiple. 

Love Hertz
Another big buyback story that investors should focus on involves Hertz Global Holdings (NYSE:HTZ), a car- and equipment-rental business. In conjunction with its fourth-quarter earnings release on March 18, the company announced that it would be spinning off its equipment-rental operations as a stand-alone publicly traded company. As a result of the transaction, management expects to receive about $2.5 billion in cash proceeds.

Most of the company's distribution will go toward paying down Hertz's $16.3 billion in long-term debt, but $1 billion will be withheld so that the company can buy back shares. This plan will replace the company's $300 million repurchase plan, and Hertz has the potential to buy back more than 8% of the business' shares outstanding.

Foolish takeaway
Based on the data provided, it looks like each of these companies is handing investors a nice reward for their loyalty. Moving forward, it's difficult to tell which of these businesses will deliver shareholders the largest possible return. But given the size of its buyback, I'd say Sirius is a nice contender. Due to its low P/E ratio, AT&T also looks appealing for the long-term investor who doesn't mind waiting for some potentially explosive returns.