Rails for sockets - SO much easier than having them in a stupid case, on which the plastic catches fall off.
CV boot clip pliers - enables you to do an annoying job properly - they're about £15 from GSF.
Bits of 2x4 (or larger) wood, NOT bricks to drive cars on/prop them up with (use caution). Bricks crumble and shatter under weight. Wood does not and is thus far safer.
Head torch - I cannot overstate how f*cking great head torches are. Use one in an evening and afterwards you'll find it annoying that when you turn your head to look at something it doesn't automatically light up.

Also I'd recommend a crawler trolley to get under cars easily and a beanie hat to stop yourself getting oil and sh*t all over the back of your head.
A good set of overalls is also of benefit - saves a lot of parent/wife-based aggro and CV grease is a git to get out of seats when you've not spotted that big gob of it on the back of your trousers.
A good supply of lightweight gloves to help keep the cr*p off your hands, so everyone doesn't glare at you in work the next day.
And a press for bearings.