I keep mine in a small Kifaru pull-out in my top pack pouch for easy access. It contains:
3x zip-ties (can fix so much with those, also make an emergency tourniquet)
1 Star Flash micro signal mirror (aimable)
1 Shoreline Marine emergency whistle (WAY louder than most emergency kits have)
1 mini emergency compass (cheap, but good - oil filled, accurate)
8x bandaids
4x 3m Steri-Strip skin closures
1x foil mylar rescue blanket
1x white cyalume snap light
1x sharpie with electrical tape wrapped around the handle
4x "surgical 2's" (gauze pads)
1x adhesive bandage, a horse leg wrap some old CPW geezer told me was better and cheaper than the ones made for humans
1pr blue nitrile gloves
1x spare pair contacts (I'm blind without them)
1 small bottle rewetting drops (can also be used as an eye flush if you get something in your eye)
3x handi-wipes
2x GasX tablets
2x Ondansetron 4mg (anti-nausea tablets, this is a prescription for me but you can get emetrol over the counter)
10x aspirin 325mg
10x caffeine 100mg
1x diabetic sugar tablet, 1000mg
4x diphenhydramine 25mg (Benadryl anti-histamine)
1 pack book matches, mostly because I keep the meds above in a zip-loc and this guarantees a backup set of dry matches
In winter I add 2x day-quil and 2x ny-quil tablets in case I pick up a cough or head cold
Entire kit weighs 7.2oz including the Kifaru bag. This is my "thrown in" for basically any hike, backpacking trip, scouting, or hunting, which is why it has both emergency and first aid items. So it's lighter than some other "pure first aid" kits but lighter than most "emergency survival kits". The only thing it's missing that a lot of other kits have is a cutting tool, but I'm basically never without at least 2-3 knives of some form or another, so I don't feel like I need an extra one in here.
Then, in my truck, I have a much larger first aid kit with more of the stuff you'd expect to see there. It has the basics like bandaids and gloves, but also adds things like ABD Combine Pads, a real tourniquet, etc.