Dog and cat poo.
Hoses snagging and folding over on themselves cutting off the flow.
Wheelie bins
Customers that know you're there and spend ages finding their chequebook when you finish and you knock for the dosh.
Locked gates with spikes or trellis on the top.
And a monthly occurance:-
The gate copper on Avonmouth Docks who waves everybody through except me and who checks inside my van - "Is it cuz I is da window cleana?"