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 ****, 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.