And by flaw I mean unremovable prediction (aka angle-snapping, drift control) or acceleration, or z-axis bug, or whatever else is fucked up for a gaming mouse in my opinion.

I'd like to make a list of these OK gaming mouses, care to help ?
So far the list is :

3 buttons :
-Microsoft WMO 1.1 (STMicroelectronics OS MLT 04).
-Microsoft Optical Mouse Blue (STMicroelectronics OS MLT 04). Out of the market.
-Razer Abyssus (Avago ADNS-S3888). (Beware : the older firmwares create a jittering issue ; as Abyssus firmware can't be updated, you have to buy a recent enough model, loaded with one of the newer firmwares which fix the jittering)
edit 11/11 : beware

5 buttons :
-Microsoft IMO 1.1 (STMicroelectronics OS MLT 04).
-Microsoft IME 3.0 (STMicroelectronics OS MLT 04).
-Razer Deathadder 3G (Avago ADNS-S3668). (you may have to update the firmware to remove prediction)
-Razer Deathadder 3.5G (Avago ADNS-S3888). (you may have to update the firmware to fix a jittering issue)
So far odds are DA 3G sensor > DA 3.5G

7 buttons :
-Cooler Master Storm Spawn (Avago ADNS-3090). (Jittering fixed since firmware 30a ; high LoD fixed by firmwares 31 and 32, but it may have introduced some tracking issues with certain surfaces. Note : CM's tech team seems pretty active.)
edit 18/01/12 : beware

8 buttons :
-Logitech G400 (Avago 3095)
Important : The first generation of G400 are shipped with an Avago 3080E sensor (or not : see here) which has prediction ; to avoid it buy a G400 with a PID above LZ13333 (located under the mouse), which packaging is different (see Chris_P -from the Logitech Team- statement here) by having a Logitech sticker looking like that (supposedly ; good luck).

Mouses without prediction (or which can be removed), but suspected of having other flaws :
-Logitech G9 (Avago ADNS-6090). Skipping ?
-Logitech G9x, Logitech G500 (Avago ADNS-S9500). Positive acceleration.
-Steelseries Xai, Steelseries WoW Cataclysm (Avago ADNS-A9500). Positive acceleration ?
-ROCCAT Kone+ (Avago ADNS-9500). Positive acceleration ?
-Mionix Naos 5000 (Avago ADNS-9500). Positive acceleration ?
-Razer Mamba, Razer Naga, Razer Imperator, Razer Disney TRON (Philips Twin Eye PLN 2032). Z-axis issue - video.
-Saitek Cyborg R.A.T. 7, Saitek Cyborg R.A.T. 9 (Philips Twin Eye PLN 2032). Z-axis issue. Click bug ?
-Razer Lachesis, Razer Orochi (Philips Twin Eye PLN 2031). Z-axis issue.
-Saitek Cyborg R.A.T. 5 (Philips Twin Eye PLN 2031). Z-axis issue.
-Cooler Master Storm Inferno (Philips Twin Eye PLN 2031). Z-axis issue.
-Thermaltake Tt eSPORTS BLACK (Philips Twin Eye PLN 2031). Z-axis issue.
-Cooler Master Storm Sentinel Advance (Philips Twin Eye PLN 2302). Z-axis issue. Click bug ?

Mouses without prediction (or which can be removed) yet to be proven flawless :
-Razer Deathadder 3.5G Black Edition (Avago ADNS-S3888, separated firmwares from the 3.5G though).
-PureTrak Valor (Avago ADNS-3090).'s thread. (edit 18/01/12 : the thread is 156 pages huge and so I don't have the courage to check what's the final verdict with this one. From a glance there seems to be some issues, if someone wanna dig in and report back that would be cool)
-Zowie AM (Avago ADNS-3090).'s thread1-2, anon's infos & thoughts.
-Zowie MiCO (PixArt PAN3305DK-H). (Note : quite low perfect control speed limit ? (1.27m/s))
edit 18/01/12 : reported having some prediction ; I'm gonna wait confirmation it can't/won't be removed by a driver update before erasing it.

Give relevant informations in the comments and I'll add them.

Relevant links :
-Skylit's awesome OCN Mouse Sensor Reference and Performance sheet (reporting, among other technical datas, which mouses have prediction).
-Optical Mouse technology review, by Richard L. Owens.
-worthless information about your worthless mouse.
-ESReality MouseScore 2007.
-Interface Device Wiki.
-Avago site.