canon 15mm f2.8 ($650)- great wide angle lens for a rebel, very sharp, not too much distortion but enough... and since it is a prime, you wont have to deal with barrel creep during high speed follow cams.
carl zeiss 50mm f1.4 ($700)- incredible lens, unmatched color accuracy, sharper than a sushi knife, great bokeh, built like a tank, and at $700 that is less than half what a canon 50mm f1.2L goes for.
70-200 f4L USM ($650)- Great light weight telephoto zoom lens. extremely sharp, very fast AF, very solid build quality, not to mention on days you will probably deem worthy to shoot on there will be more than enough light where you wont have to use low f-stops.
*besides the cost of a 70-200 f2.8L USM will get you a 70-200 f4L USM and a carl zeiss 50mm f1.4.