Editorial take: Citi Custom Cash
Genuinely clever. 5% on whichever category you spent most on each month, capped at $500/month. Earns $25/month = $300/year effortlessly. The cash back is paid as ThankYou Points, which transfer directly to Citi's airline and hotel partners at 0.7 of the premium ratio; moving them onto a Citi Strata Premier or Strata Elite account gets the printed ratios.
