In reply to azzykaii:
My own personal kit is similar to that carried by Mr Trebus, which can be supplemented by a bigger role specific kit as required. For me the key things elements are as follows:
Contains enough to deal with blisters, bites, scrapes, pains and sprains.
Is lightweight enough to be unobtrusive when climbing.
Compact overall package (as previous point).
In waterproof packaging (small Alpkit dry bag).
I am not concerned about having everything in one bag because there is so little it is easy to find what I need. Additionally, I use zip lock bags to contain things like blister plasters and any OTC medication carried.
Most of the injuries I have encountered on the hill have been heat and cold injury (burns, blisters, heat exhaustion, hypothermia); cuts and grazes; bites and stints; and sprains. Oh, and plenty of cases of injured pride!!!!
I have been fortunate not to have had to deal with major trauma on the hill, and there is a risk that this has impacted upon the kit I carry. I suppose it is said that we are shaped by our experiences. It's the same for my first aid kit.
I have owned a number of off the shelf first aid kits over the years and have generally consigned them to one of the gear boxes in the garage after using the same items from each. Gloves, plasters, and tape. Pretty much every thing else remains unused.
As other posters have stated the key thing is having appropriate the knowledge and being confident to apply it to adapt other items carried.
Of the more 'specialist' items available, a Sam splint is a very useful piece of kit.