bare bones rack trunk
 

stripped my rack trunk and started from scratch. not much in there!

tube
2 levers
patch kit
pressure gauge
mini hand pump
3 quarters
multi tool
swiss army knife
needle nose locking pliers
2 zip ties
tube of acetaminophen; ibuprofen and aspirin

Of the things you mentioned the only one I have in my rack trunk is the 3 quarters - sometimes. Depends on if I have change in my wallet's little change pocket. My rack trunk is for wallet, keys, unused lights, extra batteries, cell phone, lunch, change of clothes, toiletires and whatever else I might need to carry to/from work or on a ride.

tube
2 levers
patch kit
multi tool
needle nose locking pliers
2 zip ties
^
These are all in my seat bag.


pressure gauge
^
Don't have one except for on my good floor pump at home. I use wide enough tires that I can just eyeball this in a pinch if changing a tube on the road.


mini hand pump
^
Mounted on my frame.


swiss army knife
tube of acetaminophen; ibuprofen and aspirin
^
Will probably be in my panniers when I tour, but not on my commute.

I also added towel and washcloth; change of clothes; underwear, plus a pair of shoes which I will leave at the office.

stuff I left at home:

2nd tube
10 lbs of wrenches ... hahahaha seriously!
rubber gloves
chain tool
spoke tool
shower cap
hockey tape
electrical tape
4 extra AAA batteries
spare headlight
extra batteries for the spare headlight
6 other quarters ... hahaha seriously! wtf!

there's probably other stuff in the old rack trunk I forgot to mention here! good grief!

If you have a mini-pump there is no need for a pressure guage - you just pump till you are exhausted, and then it is only just enough to get you home. The swiss army knife is not much use for bike fixing, but I have used mine for sawing low hanging branches over the bike path.

What are the needle nose locking pliers for?

I like the pressure gauge for when I get to a real pump then I can get up to MAX pressure.
I like the philips head on the swiss army knife. it also has scissors and tweezers, small regular head screwdriver etc. It also has one large blade for those grizzlies that aren't scared of my shear mass ... :P
Yeah, those needle nose locking pliers ... good for pulling cable and snapping chain back together. also good for weird little nuts like on my rack and DR, etc.

Dunno, I just did a quick strip down and grabbed what i thought I should have. I'm usually picked for a century regardless is it's a 13 mile commute or a 65 mile dinner time ride, oh and yeah the stray century ... I dream of riding with no rack and no rack trunk - but it's just a dream. :-)