绕口令 (ràokǒulìng, "mouth-detouring commands") are not party tricks - each one isolates a contrast Mandarin learners actually lose. Slow first, then speed; the tone is the drill.
The canon
四是四，十是十，十四是十四，四十是四十。 - sì vs shí, the dental s against the retroflex sh. The eternal drill for that contrast.
妈妈骑马，马慢，妈妈骂马。 - mā/má/mǎ/mà: four tones on one syllable in one breath. The classic proof that tone carries meaning.
红凤凰，黄凤凰，红粉凤凰花凤凰。 - hóng/huáng/fěn/fēnghuáng: initials h/f plus vowel juggling.
吃葡萄不吐葡萄皮，不吃葡萄倒吐葡萄皮。 - chī/tǔ/pí/pú alternating; also a rite of passage every Chinese kid recites.
How to drill them
Read once slowly with the characters, then from pinyin, then from memory - the point is your mouth, not the page. Mark every tone before starting; tonguetwisters punish tone-blindness first and consonants second. The games and tongue-twister pill decks have them with native audio, which matters: you cannot drill a twister you cannot first hear correctly.
Why bother at all
Tongue twisters exaggerate exactly the contrasts that blur at conversational speed - s/sh, n/l, tone pairs. Two minutes daily on one twister beats an hour of passive listening for articulation.
Three more to try
牛郎年年恋刘娘 - n/l alternation (niúliú vs liáng's n/l collision), famous in the south where the distinction blurs. 坡上立着一只鹅，坡下就是一条河 - the e/o/ê vowel ladder. 天上一颗星，地下一块冰 - ing/ing front-back nasal pairs. Each still isolates one contrast - pick the one matching your weak pair and drill it until it bores you.
Common questions
What is the most famous Chinese tongue twister?
四是四，十是十 (sì shì sì, shí shì shí) - "four is four, ten is ten". It drills the s/sh contrast every learner loses.
Do tongue twisters help with Chinese tones?
Yes - 妈妈骑马 māma qí mǎ forces all four tones on the same syllable under time pressure, which is exactly the skill real speech needs.
What is a 绕口令?
The Chinese tongue twister - literally "mouth-bypassing command". They are a folk tradition: short phrases engineered around a single hard sound contrast.