Depends on what your price range is - and where he is at in the process/what he could use most moving forward..... I just started making wine recently and have made many afternoon stops at the supply store and online shopping/building my supplies..... A couple ideas that popped into my head as possibilities:
- a basket of supplies, ie: K-meta, Sorbate, Tannin, Acid Blend -- those little things that are used and good on the shelf (like a chef's spice cabinet)
- Kit of a wine he likes, or one he may want to try making (if he makes kits)
- New Carboy so he can start another batch
- All-In-One-Wine Pump - probably my best investment after my initial kit of supplies.