What first aid equipment is on a commercial aircraft?
Obviously, first aid kits have items that save your life. The contents of the First aid kits or Emergency medical kits (EMKs) vary based on the jurisdiction. For example, FAA requires the following items 


  ... on all airplanes of air carriers operating under part 121 for which at least one flight attendant is required. EMKs and AEDs are “no-go” items and must be carried as indicated on the Minimum Equipment list.




Contents of EMK; table from FAA Advisory Circular 121-33B Emergency Medical Equipment.

On the other hand, Indian DGCA requires the following items in first aid kits:





First Aid contents; table from DGCA Document No: F No. 11-690/CAR X-II/2010/AI(2) Provision of Medical Supplies in Aircraft

Most of the requirements are broadly similar, while there are some region (or country) specific differences; for example, DGCA requires rehydration solution to be carried, presumably due to heat. FAA, on the other hand requires Automated External Defibrillators (AED) to be carried for aircraft with payload more than 7500 lbs (DGCA requires it only in international flights of over 2 hours).