Our choir sings the Viadana "Exultate Justi" and the Palestrina "Sicut Cervus". The middle section of the Viadana is a real tongue twister - first 'in psalterio decem chordarum' and then 'in vociferatione' . . .
Another great one is the Palestrina Magnificat Primi Toni (Liber Primus). We sang this for Archbishop Donoghue's vigil/vespers the night before his funeral.
Yes,we do share some favorites! I learned these pieces through the talents of the various choir directors our school has had through the last several years - I never knew there was such beauty out there - (and yes I agree with you on the Exultate - I feel like a trapeze artist on some of those lines too :) )