I've come into some money and DH is insisting I flitter away a little on a Forever Bag. I only wear cross body bags.
I have two I've always adored but can't choose between them!
First is the Louis Vuitton Speedy 25 Bandoliere (in other words, on a strap)
Pros:
Light as a feather
Fairly waterproof/bombproof in this check version despite being coated canvas. I wouldn't have to be that careful of it.
Is basically a big bucket so can hold lots.
Holds big resale value so could be passed down to my daughter or sold at any time.
Cons:
The strap needs breaking in
Is Louis Vuitton so perhaps a bit knobby for the countryside where I live! 
Opening is a bit small though not sure that'd bother me as I don't tend to carry very bulky things like coffee mugs.
More expensive than the other option.