While Borg and Cybermen make the most sense for marketing reasons, I've been busy dreaming up scnarios in which TNG characters are stuck fighting Who aliens.
Like if the Weeping Angels showed up, they could disable Geordi's Visor and he'd have no defense against them.
Or Worf against a Judoon, and for some reason their universal translators aren't working.
Worf: "Daj ba'wi! SosChi gint'ya!"
Judoon: "Sco po fo no wo jo bo ko!"
Then Worf charges toward the Judoon with a bat'leth.