Your top 3 "bang for buck" lenses?

Canon EF 100mm/2
Canon EF 70-200/4 USM Non-IS
Canon EF-S 15-85

Canon 17-40 . . . FF only
100 2.8 macro non-L
200 2.8

Canon 15-85 IS USM
55-250 IS
60mm Macro

Of course, I'm quite biased, as my sig will reveal

For FF:
85 1.8 or 100mm macro (have both, and often hate the fact that I need both, but they are both awesome)
17-40 (I like UWA and it's simply the only budget-ish option).
Tamron 28-75 or Canon 28-135 are decent options paired with a 5Dc, but I opted for the 24-105L

For crop (previously my most used 3 anyway)
Tokina 11-16
Canon 28 1.8 (perhaps a sigma 30 1.4 if you're lucky or have MA)
Canon 100mm macro again

I am assuming that bang for the buck has to lean heavily towards the amount paid for any piece of equipment, while retaining a good amount of consideration for IQ. For this reason I can't include my 100-400L, or my 10-22, here because they simply cost a TON of money. Here is my 'bang for the buck' list.

C/Y mount:
Yashica 135 f/2.8 MLc, got it free with a broken FX-2 for $29!
Vivitar Series 1 28-105 f/2.8-3.8, $15.50.
Vivitar Series 1 70-210 f/3.5, $59.99.

Some of the Yashica ML lenses were made at the same time, in the same factory as Carl Zeiss lenses. Is that significant? I don't know. Yashica YUS and DSB lenses are not in the same league. I have a closet full of each.

EF mount:
EF 28-105 f/3.5-4.5, $129.
EF 70-210 f/3.5-4.5, $102.
EF 50 f/1.8 ii, $98.

I have other EF glass that gets more bang (better IQ, wider max aperture, faster focus) but each of them cost considerably more bucks. This list represents my best value per dollar spent lenses.

nifty fifty
EF-S 55-250IS
EF 28-135IS

Full-Frame;

Canon EF 50mm f/1.8 MkII

Samyang 35mm f/1.4

Canon EF 100mm f/2.8 non IS

Another vote for the Samyang 35 1.4.

Also the 50 1.8 was such a blast to use when starting out.
And lastly, the 24-105L.

24-105L ,100-300 L and my 50 1.8 a distant second. =)

Sigma 50mm 1.4
Canon 135L
Canon 70-200 f4L IS

Sadly I only have one of these three left in my lineup.

FF
Canon 85Lf1.2mk2
70-200Lf2.8mk2

My 3 choices:

EF 50mm f/1.8 II
EF 24mm f/2.8
EF 100mm f/2.8 USM Macro

All relatively cheap; all decent performers for the money. You could possibly switch the 100mm Macro for an 85mm f/1.8 or 100mm f/2 if you don't shoot macro.

Tamron 17-50 f2.8 non image stabilized version
Sharp, inexpensive f2.8 through entire range, good colour

ef 85mm f1.8 usm
Fast auto focus speed, 1.8 aperture & great price)

ef 100mm 2.8 usm macro
Versatile, fun lens at a great price.

Tamron 70-200 f2.8
Sigma 24mm f2.8 (old film version: no adjustable aperature and loud AF, but compact and gets the job done!)
Canon 100mm 2.8 macro

All FF:
-Zeiss 135mm f/3.5 Jena with cheap M42/EF adapter
-Samyang 14mm f/2.8
-Canon 28-135mm (IQ pretty much at 24-105 level but build is not)