First, in case it matters, I'm female.
I got quite a few Cross pen & pencil sets, some of them engraved. Can't say I ever used them but a nice pen that's comfortable to use (the Cross ones I received were not) would be a good choice. A nice watch is handy.
I got a few "nautical" items -- pictures, ship's clock, bookends, etc. Couldn't use them at USNA but could in my home four years later. Still have a few of them.
Received a few books of various sorts. Flowers. Picture frames were popular. A few items of jewelry, such as silver and gold bracelets (gold was cheaper then!). And, yes, cash and savings bonds (the latter was good idea at the time, not so much so today).
While money is great and very useful
, some people like to give "things" that will last a long time. In all honesty, there's not a lot you need while at USNA that the military won't give you. So, think about things that come in handy on vacation, such as IPods, video games, movie tickets, sports tickets, etc. or think long term -- mids will eventually graduate and have an apartment/house and need stuff. Women are probably a bit easier, b/c jewelry (real or costume) is always an option.