The best replacement for regigigas is giratina.

The best alternatives to regigigas are rated as following:
★★★★★  giratina
★★★★★  heatran
★★★  regirock
★★★  groudon
★★  regice
★  registeel
  slaking

Your alternative for regigigas is not listed? Suggest!
Speaking about regigigas, one probably shouldn't forget about regis.

Other search terms related to regigigas and their ratings are:
★★★★★ regis
You have in mind a companion for regigigas and it is not yet here? Propose!



Google Trends

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regigigas
giratina
heatran