To relieve stress on the winch and cable while plowing you can attach a snatch block to the top of the blade then feed your winch line through the block then up to the rack. Makes it a straight pull so you're not wearing the winch cable. The snatch block comes in handy all year.
Synthetic winch line is much easier to handle, does not draw blood like steel cables, and it floats.
Hand/thumb warmers wired to work only when ignition is on.
Pretty sure Can Am's won't run with a dead battery so adding a digital voltage meter is a cheap and easy way of monitoring the charging system and battery. I added one to the handle bars and is very small at roughly 1 1/2" x 1/2".
Tree saver/recovery strap so you're not damaging trees with the winch line. Also useful for towing (do NOT use your winch for towing) and attaching the winch line to odd shaped or easily damaged objects.
Front and rear hitch or tow strap.
Aluminum skid plates for the frame and A-arms.
Left hand throttle control, either Goldfinger or DIY option. One of the best mods added to an ATV.
Basic tool kit with wire, pliers, knife, ratchet, screw drivers, zip ties, etc. Sometimes you'll need to remove whatever is left of a broken axle to continue riding, remove a spark plug to get water out of a swamped engine, switch batteries with a buddy who has a machine that will run without a battery, cut off wire or other junk people have left in the bush, etc.