First Transpennine Express have a 50% off offer on all advance tickets on any TPE route for anyone who matches any one of the following 3 criteria:
You are age 16-18 - select 16-18 under railcard option (no railcard needed although you must have ID on you)
You get Jobseekers Allowance (Railcard needed - Jobseekers can get a Jobcentre plus railcard from their local Jobcentre Plus office. It is free of charge and last for three months) - Select Jobseekers TPE DIS under railcard option
You have a 16-25 railcard (normally only 33% off) use promo code Tpestudent - 16-25 railcard needed.
TPE routes only. All tickets have to be booked online and not the app or so it says on the website - although I managed to book a TPESTUDENT m-ticket with the app and got the discount. In the app you can put in the promo code under railcard option but you must also select 16-25 railcard for it to work.