A few hits for our one year olds with older siblings were:
Step 2 Up & Down Roller Coaster - can be used inside or out
Plasma Car - older ones rode with her at first, but she quickly got the hang of it
Shopping cart - they loved pushing their stuffies around or cleaning up toys w/it
Dress up clothes/costumes
Outside play structure - can often find practically new on Craigslist
Bounce Around (bought this when the older two were toddlers, but they all use it now)