If you regularly travel by rail you will all know that you are eligible for the

Senior Railcard which costs £30 p.a. and gives 1/3 off tickets(outside morning peak)  or if you order it on-line £70 for a 3 year card

Possibly less well known is the Disabled Railcard which costs £20 p.a. and allows 1/3 off all travel and 1/3 off the ticket of the person who accompanies you.

Details of entitlement can be found here.   Probably not well known is that if you wear a hearing aid you qualify (check the details )