These probably count as crack ships, but here's a few:
Femme!Vamprah x Krika
Femme!Chirox x Mutran
Gorast x Teridax (incredibly one-sided, though)
And the grand one: Roodaka x Lariska.
Also Huki x Macku, Hahli x Jaller, and Gavla x Tanma, but those aren't as exciting.
I don't know why, but I don't really ship any of the toa amongst themselves, aside from Hahli and Jaller.