Grange Park - dog lovers heaven!!
While I can't say I do a lot of sitting around Grange Park in the winter, in the summer you can find me there sitting on a park bench, drinking Starbucks passion ice tea, and watching the dogs (longing that I had my own!)
The park has quite a few benches, so I can always find a free one. Even if dogs aren't your thing, there are also regularly tightrope walkers (I've seen them a handful of times!), and generally great scenery to look at, including the back of the AGO which owns the park. There is also a small playground.
While I don't feel like I want to spend a lot of time there at night, alone - I will walk through it without hesitation - I've never felt threatened or in danger while I'm there. As I said, I wouldn't want to hang out in a dark corner of the park, but I feel that way about all parks at night - this one is not any sketchier!