Either the Canon 80-200mm f/2.8L lightly used for $300 and change or the 70-200mm f/2.8L IS USM new for $2000. Mostly photojournalist style work using available light only a lot. I'll probably shooting stopped down to f/4 when I can.
Also, the 17-40mm f/4L lightly used for $300 and change or the 16-35mm f/2.8L for $1400 new. Same situation here, except I'd probably keep the 17-40mm at f/4 instead of stopping down anymore.