Chinese character pairings having matching Pinyin letters but different tones

• fūfù 夫婦 (a husband and wife)
• gōnggòng 公共 (public)
• jījí 積極 (energetic)
• māomáo 貓毛 (cat hair)
• rènrén 認人 (to recognize people [said of babies])
• shìshí 事實 (fact)
• xiǎngxiàng 想像 (imagine)
• xìnxīn 信心 (confidence)

The Pleco Chinese dictionary app, with its Wild search capability, could straightforwardly find all such possibilities, but these are examples that are common enough that I could come up with them while, e.g., idling in the supermarket.

Quasi-similar:
Chinese expressions having 2 or more syllables and matching Pinyin letters, but different tones