Hello,
On my '06 Pontiac Solstice, the battery is behind the front wheel as part of trying to get the weight balance right, which doesn't sound too bad -- except to get the battery out, the front fender has to come off. You could also remove the inner fender and do it that way, I'm told.
Upside is that my '06 has, I think, the original battery in it.
My mother's '96 Chevy Lumina battery is awkward since it's under a fender brace.
My 2007 Subaru Outback H6 has been pretty easy to work on for just about everything, except the spark plugs. The front four were easy, and the back two should have been -- except the frame rails pinch in towards the back so there isn't any room. It's doable but a royal pain. The car was built with iridium plugs ($11ish each) but they're supposed to last a long time.
For non-routine-maintenance, that '99 Olds Bravada (an AWD S10 Blazer, basically) had a heater core that was awful. To remove, the dash had to come out, the inner fender had to come off, and a hole had to be cut in the heater box (it was marked "cut here" on the box!) so you could remove one fastener laparoscopically.