I've rotated a bunch. I can't comment on travel cards, but the best one I've found is Discover IT. 5% cash back on rotating-yet-useful categories. On top of that you can use those rewards to get discounts on gift cards. Home depot offers a 10% discount on cards. So you could really get a nice stackable discount.
And when a category isn't in that quarter, I'll use another card like Capital One Savor for 3% back on all dining or the Citi Premier which offers 3% on grocery and gas.
However, Citi's rewards are shit, and they offer less value if you use it to credit back purchases. If you want the FULL value of your rewards they make you jump through a lot of ui/ux nonsense to do it and that pisses me off (a 8digit one time pass code and various "next screens" just for that reward? FU).
A sleeper card, if you like their stuff, is the Gap card. A decent brand card on its own, but the real benefit is they offer these monthly spend-offers where if you spend $500 outside the brand you get $50. That's a 10% reward, just to use it for you normal stuff like gas and grocery. And an even more insane deal, they sometimes offer a deal where if you use the card 5 times outside of the brand you get that $50. So five packs of gum at the gas station (separate bills of course), gets you like a 500% reward lol. Granted you have to use the rewards on that gap brand.. but almost anyone can find use for something of theirs (old navy and BR, too). I probably get about $400/year worth of "free" Gap clothes this way.