St John Ambulance First Aid (100,000+ downloads)

Will give you first aid advice and help when dealing with an emergency. Also great for occasionally being able to recap on a first aid course you have done.

Diseases Dictionary Medical (500,000+ downloads)

This is a detailed log of all major medical conditions and diseases. This can be downloaded and used without an internet connection so idea for use on the go. 

Figure 1 (1,000,000+ downloads)

This is a forum like app for any medical case, posted by medical professionals. Can help with recognising medical data e.g ECG's or MRI scans. Does contain graphic content so be prepared. 

Nursing Manual

A quick reference guide for nursing information. Has quiz questions so you can also put yourself into real life scenarios. Also contains calculators e.g BMI calculator.

 

These apps can best used when you have 5-10 minutes to spare and just need something to do. its very impressive at interview if you can comment on a medical condition or a treatment you have read from one of these apps.