Canon's fisheye zoom can do both full-frame and circular fisheye images. A zoom-limiting switch ensures that the corners of the image don't get cropped when it's used on an APS-C body.
Standout Spec: It doesn't get much wider.
Hands On: Canon 8-15mm F/4L Fisheye Zoom
Hands On: Canon EF 8-15mm F/4L USM Fisheye
SIGMA 8–16MM F/4.5–5.6 DC HSM
Sigma 10–20mm f/4–5.6 EX DC HSM
Sigma 8mm f/3.5 EX DG Fisheye
Canon EF-S 10-22mm f/3.5-4.5 USM
Canon EOS 60D
Canon EOS Rebel T2i
Canon EOS 7D
Canon EOS 5D Mark II