Hmm...over the 5 or 6 years, things I've use in my Hobies that I can't do without:
1) Hobie Gear Bucket -- the one that fits in the hatch just in front of the seat. It really is the perfect ergonomic arrangement for tackle for the fishing I do, anyway. My mind boggles when I see folks with 4 or 5 plano boxes stuffed in a crate.
2) One of those freezer 'tote' bags. Get them at Sams Club, BJ's, WalMart...about $10. (this is either a fancier or overpriced model http://www.keepyourcooler.com/freezertote.html
) Drop a few frozen bottle of water, fold it flat and it's the perfect fish storage solution.
3) X-tools fishing pliers. You can get these foam-handled tools online or sometimes in WalMart or other sporting good sections. They're cheap, visible, they float and they can cut braid.
4) Deluxe cart: Yeah, the set is $190 US. But they work. <sigh>
Things I thought I'd use but have/had no use for:
1) Anchor. Just never needed one. Easy enough to hold approximate position without the hassle and tangle to say nothing of needing an 'anchor trolley'.
2) Stake-out pole. As above. Just never used it often enough to bother taking it with me.