Singles out one particular case as special or exceptional. It has two flavors: (1) 'only/especially this one' to express confidence ('my child, of all people, would never…'), and (2) 'of all times/things' to lament unlucky timing ('on the very day I needed it, it broke'). にかぎり is a formal variant meaning 'only for this case'.
[Noun] + にかぎって/にかぎり
うちの子にかぎって、そんな悪いことをするはずがない。
Uchi no ko ni kagitte, sonna warui koto wo suru hazu ga nai.
My child, of all people, would never do such a bad thing.
にかぎって singles out one's own child with confident trust.
急いでいる時にかぎって、電車が遅れる。
Isoide iru toki ni kagitte, densha ga okureru.
The train is delayed precisely when I'm in a hurry.
にかぎって laments the unlucky timing of the very moment concerned.
本日にかぎり、全品半額です。
Honjitsu ni kagiri, zenpin hangaku desu.
Today only, all items are half price.
にかぎり restricts the offer to this one day ('only for today').
• The '〜時にかぎって' pattern usually voices frustration at bad timing. • The 'うちの子にかぎって' pattern expresses firm confidence in one person/thing. • にかぎり is the formal 'only for this case' variant seen in sales/notices.
The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones にかぎって is tested against.
にかぎらず means the opposite — 'not limited to'; にかぎって singles out and limits to one particular case.
だけ neutrally means 'only'; にかぎって adds emotional emphasis (confidence or lament) about that one special case.
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