You probably found the most important ones. Although the rope gun is so powerful, if you found that one you can get by without some others.
Anyway here is a list:
Spoiler alert!
Starting out in your inventory: homeblock
Every room has a map coin (39 to 44 total)
Every room also has a vending machine
Bubble spirits don't actually matter. 14 quotes in the world, 7 story pieces on Mount Hop
Other story items:
postcard
ancient maze scroll
Power ups which affect movement:
double jump suspenders
rope gun
parachute
flippers
scuba tank
wall jump socks
climbing belt
slide grip gloves