what to buy a guitarist for his birthday?

hey guys and girls, i need a little help.
my boyfriend's birthday is coming up and im not sure what to get him. it's his 40th so has to be something good, i thought of a foot drum but im not sure. asking me what compliments a guitar is like asking stevie wonder what colour curtains he likes best!!
so, here's a bit about him to help you help me.
he plays mostly acoustic guitar but it plugs into his amp to if that makes a difference,
plays some spanish guitar, some classical and some stuff i dont know anout but it sounds good!!
he has a takimine, an ovation and a spanish guitar but has had fenders, gibsons, etc in the past,
he likes ac/dc, judas priest, metallica, iron maiden, the levellers, show of hands, newton faulkner, dick gaughan, rory gallagher, i am oak,dodgy, 4 none blondes, bjork, juan martin, gordon giltrap, pierre ben susan....a little bit of everything really.
im not sure how much of this helps but you can ask any questions if you want to.
he is a quite advanced guitar player, he plays a song called 'farewell to michael' and lewis and clarke'
please help if you can because i am clueless.
thank you in advance.
jo