Bic Phone (Spain) for €19 including €12 credit
 

From the makers of those nice simple pens, comes a nice simple prepaid phone. This has been around for a while in other countries, but I only recently saw it available all over the place here in Spain.
El móvil 100% listo para usar. - BIC phone - BIC® phone

It comes with an Orange prepaid SIM and €12 of credit. You can pick it up in plenty of gas stations, and small corner shops. However, it's not for sale at €19 everywhere, as I recently saw it for sale in a motorway petrol station for a higher €29. Not sure what all that is about! :(

Also worth noting is that they have a €6 per week plan for calling other Orange phones and landlines for free. This is somewhat unique in Spain. Also, unlike other operators, they do not charge you a connection fee for these calls. It can be very useful for calling the access number of Betamax for example.

However, it's actually only on weekends where you can make as many calls as you want at any time. During the week, you are restricted to off peak times only (18:00-08:00) and also limited to only 100 mins total. Outside these times, you pay 18c/min and a 15c connection fee.

More details here:
http://www.bic-phone.es/docs/Tarifas%20de%20Prepago.pdf