There are some people who it is just very difficult to buy for because you don't know them all that well personally.  Many people who have kids playing organized sports sometimes feel as though they should get their child's coach some type of gift.  I was searching around for football coach gifts and I think this is a pretty good list of ideas.

There are a bunch of great items if you follow that link above, but there are many football themed items that you can buy as gifts for coaches without breaking the bank.  This book, The Football Coaching Bible might do nicely.

Some other ideas include books written by well respected, professional coaches who have spent years climbing their way to the top of the coaching profession.  You can never have enough words of inspiration I suppose.

If you think the coach might enjoy a little bit of everything, you could find a very nice football themed basket that would actually be great for any guy who enjoys football. You'd figure that the coach has some interest in the sport, so it might make for a nice gift that probably won't be duplicated by anybody. Even if it is, the stuff in the basket probably won't go to waste!

If you don't like either of those gift ideas, just check out this more thorough list of football coach presents

Of course, don't forget that just because he coaches football, he might still have some other outside interests.  If you happen to know what they are, you can base the present you choose on that.  If you ever talk to the people he coaches with, or his family, they might be able to give you a different perspective of what he might enjoy receiving as a gift.