I have one of these awkward things too!
So far I have on the list (or bought by myself or grandparents!):
Turtle Beach headphones for his xbox/pc (£35)
Xbox live
Bench gift set (contains a pair of boxers - he'll love this!) from Boots (£10 though on 3 for 2)
Sam Smith's Album
X box games (leaving those to DH to purchase suitable ones...
)
Box of sweets and different chocolates he likes.
Superdry Hoodie
Converse
His main present is a sofa bed from Ikea for his bedroom - he knows about this and is excited oddly!.
I've also got him a few bits of clothes, but not expensive ones - just trendy bits I know he will like.
Trying to find him a cool belt too.
His birthday is in March, so I have to go through all this again soon! Arghhhhhh!
Liking the other ideas on here too - never heard of Blockopedia, but he plays minecraft, so I think I'll get him that too! Thank you!