Horses on small sandy soil will clear grass so well you won't have to worry about mowing.................... anything.... ever...... hehe
Geese are good grazers, but in small areas their poo can get overwhelming
goats eat weeds and anything you DONT want them too
My sheep was starving 24 7, no matter how much he ate
My minis graze well but it takes a lot of them to keep grass down
Don't know about my mini cattle yet - horses ate all grass
llama & alpaca are sorta like the minis, might be good in smaller areas or larger numbers
Emu graze here and there
Swans graze but less effective than geese
peafowl eat fire ants and some plants, not really grass too much
That's about the extent of my animal knowledge with grass or lack there of.