Men are usually attached to gadgets.You can give him any kind of small non electronic gadget or tool.It may be dependent on his taste.

Other choices include

  1. A good book of his interest.
  2. A good T shirt.
  3. A pair of goggles.
  4. A DVD of nice movie.

Things to avoid

  1. All feminine things, like flowers, perfumes,romantic novel.
  2. Accessories related to grooming.
  3. Things which are personalized like mobile phones,watches,wallets etc.

The idea is to give him some thing tangible,which will remain with him all the time (Either physically or mentally), which recreates your presence even after you are not there.A good quality key ring is also a better idea.All this is, off course dependent on your man’s taste.