Road warriors like you need plenty of flexibility. You never know when your boss sticks you with last minute expenses at the copy shop or at the hotel front desk. And, if you lose the next round of restaurant credit card roulette, you don't want your card declined in front of colleagues or clients.

That's why I'll suggest a few rewards credit cards without pre-set spending limits:

• American Express® Premier Rewards Gold Card. The classic charge card got a modest facelift not long ago, adding some perks to ease your time on the road. Membership Rewards points for eligible purchases can help you earn points toward air travel and access to exclusive events. Upgrade to a Platinum Card® from American Express if you want to gain access to airport lounges around the world while earning even more points.

• Chase Freedom® Visa . This easy-to-track cash back rewards card pays you 1 percent for every transaction you make, all year long. You can even earn up to 5 percent in rebates when you sign up for seasonal rotating categories.

• Citi® Platinum Select® / AAdvantage® Visa Signature® Card. If "on the road" really means "in the air," Citi's premier airline credit card lets you earn miles redeemable on one of the country's best-connected route networks.

Keep in mind that the phrase "no pre-set spending limit" doesn't mean you have an unlimited line of credit with any of these lenders. Every time you swipe your credit card, your lender's database compares your purchase to similar transactions you've made.

If what you're buying falls too far outside your expected pattern, or if it looks like your purchase could put a strain on your budget, you may get declined. Therefore, it's a good idea to let your bank know of any unusual travel plans or big purchases in advance.