Just a quick question.

What kind of things does he like?

His age may play an important factor as well,is it a landmark birthday?

And finally,how long have you been going out?

Have to spread the rep...
I agree with what redhed35 has suggested.

21 is a landmark birthday!

How about a night in a posh hotel?

Tickets to see his favourite band,sports team,concert,car racing,bike racing.

A flying lesson, a musical instrument? Plus lessons.

Driving lessons.

'for his eyes only' outfit for you to wear.

Tickets to a beer festival.

Something for his car,if he's into cars.

New speakers for his music system.