Cleaning/de-greasing fluids - Gunk/Jizer, Jenolite liquid, White spirit & hand cleaner are all useful.
Note: Using washing up liquid, for example:- when fitting rubbers or tyres is not recommended as these detergents contain salt and we all know the effect this has on steel. Try talc or use tyre soap.
Aerosol spray paint in gloss black, satin black, clear lacquer & silver wheel paint are another must have.
Wellseal v silicone - for the crankcase gasket. Wellseal remains liquid & does not harden with age, advantages being no need rush the re-assembly task in hand. Silicone will harden giving less chance of it seeping into the oil. Use either compound VERY sparingly - stories of blocked oil screens & oil jets wrecking engines are quite common place.
Wellseal - Also recommended for the cylinder barrels/head gaskets, I didn't bother and my head had a small oil leak from the cam chain area, now fixed.
Compressed air - aerosol sometimes referred to as an 'air duster' is very useful when working on the carbs and engine oilways.
Protection - Goggles, rubber gloves & dust masks are another must have. Petrol molecules penetrate the outer skin and can cause liver damage!, Used engine oil is slightly carcinogenic.