I believe there's not a more quintessential piece of classic sportswear than the rugby (aside from its sartorial cousin, the polo). These days, most rugby teams don skintight synthetics, but nothing compares to the real thing. A well-constructed rugby will last decades, with sturdy cotton twill that can really take a beating. Whether working around the house or working your way from a scrum, you should not be without a few, in classic rugby stripes like those shown above. Barbarian Rugby is perhaps the finest choice for authentic pieces, and Canterbury of New Zealand is great as well. The Polo rugby has always offered the perfect fit for me - trim cut, good sleeve length, and excellent durability. I've taken several through scrimmages, and they've held up as well as my Barbarian hand-me-downs.
Polo puts out a number of basics each season (aside from the Big Pony monstrosities), which can be picked up around $30-$40 on clearance. Stocking up for summer, I snagged the rugby shirts pictured at a Macy's sale for $24. For an even better deal, hit up your local thrift shop or eBay. On eBay, you'll find vintage pieces from brands such as Barbarian, Lands' End, Umbro, and Izod for practically nothing.
Go in for a scrum, chum.