Most guys love computers, so a model such as a MacBook Pro is a great gift idea, especially if he is a creative type. If that is too costly, then think inside that same technology ballpark; perhaps a low-cost tablet computer, for example.
A practical gift is a leather belt in a color that goes with most items, such as a basic black or brown. The beauty of this type of gift is that can be expensive or inexpensive; scale up in material, for example, choosing an exotic animal skin or top-grade leather, to really blow the giftee away. Similarly, a dopp kit, or bag, especially one in a different fabric or pattern would likely be greatly appreciated, because he can carry it with him to the gym or on trips.
Almost every guy loves jeans. This fact makes buying the man of the hour a pair of jeans an easy call. A heritage brand like Levi's tends to make styles that stay current over the years and through all the fads, which makes them a good investment. Another brand that has stayed relevant over the years and that does not seem to go out of style is Converse Jack Purcell sneakers. Both of these gifts have the added benefit of being less than $100.