There has been a lot of suggestions on here, very good ones which I read but here's my view on attachments. Since you have a lawn tractor with a snow blower, your in my opinion wasting your money buying attachments for the tractor to clear snow. A rear blade is very useful with clearing snow but it also throws gravel off a gravel drive and isn't as good as a blower in my opinion. I assume you don't need a mower also since you have a seperate garden tractor like I do myself. So the question you should ask is what is the next thing you need that would most benefit you with the tractor that you can't do with the garden tractor.
I have found the tool I use the most on my tractor is pallet forks, actual pallet forks, not clamp on, I use those all the time for moving stuff ext. so for general usefulness I would get pallet forks for the FEL. If you have a gravel drive a land leveler or land plane is the fastest and best way to grade an existing drive, if your gonna be digging new trails, a box blade would work better. Rear blades are cheap and can be bought used for next to nothing, like one guy on here said, go out and find the heaviest old blade you can and repainted it, those old blades are much heavier than the new economy blades.
For general use:
1. Standard duty Pallet Forks
2. Land Plane or box blade (6-7ft)
3. Heavy used not bent rear grader blade (7ft min)
4. 3pt Logger duty Boom pole (for dragging logs if wooded)
I would never own a 3 point
chipper or FEL grapple root bucket, I think unless money is no option there not that much help and aren't used enough, Keep in mind that many dealers rent attachments also, so unless you plan on using it a whole lot, just rent one and take it back the next day.
In my mind it's all about efficiency for each job I do, I find that some jobs are more efficient with different things like you won't gain by getting a blade on the tractor to push snow when you have a blower, if your doing firewood it's faster to throw the chunks in the bed of a truck or on a trailer than it is to grapple it and load it with a tractor ext.
If you plan on making a garden your best bet is a 3pt 2 bottom 12 or 14in plow and a 6ft-7ft disk, (I don't think you have enough weight for a 3 bottom plow, HP isn't the issue, it's weight and tires, R1 tires maybe) that set up I feel would last longer and do just as nice of a job as a tiller, tillers are just easier and more convenient and also more expensive and more maintenance, if your breaking new ground on a tiller you will most likely be sheering bolts every time you hit a rock or hard spot and if you don't have sheer bolts you can do major damage to one in a hurry. Plows are more primitive in a good way.
Another thing to look into is a brush hog if you have pasture you don't mow on a regular bases, but if your only using it a few times a year, renting one will work well also, that way it's not sitting around rotting any you get one in good working order every time. We all can give you options on what to buy but it's really up to your needs and what you can buy to get the most use out of the tractor.
