Wow, this list what i have waiting for. Thanks to all who contributed.

My experience so far

Do accept:
Restaurant: Room Eighteen 拾八风味, Ying Ker Lou 迎客楼 (Minimum RM50
)
Stores: Ikea
Online: Paypal

Don't accept:
Bookstore: Popular (What?!!  )

May i ask how to pay DBKL with Amex? Over the counter or online payment?

Even if Starbuck accept AMEX, I shy pay for a cup of coffee with it. I usually just flash my HSBC Platinum CC and get 10%. If you got JJ card, also can get discount but I know you don't 

same goes to perodua sc

for Starbucks , not sure if can use together with Staff B-Card and get additional 18-28% disc...LOL

Just found out that AMEX can be used at my favorite Lowyat store, VIEWNET. 

Glad Sounds also had a Amex sticker/plate at their door but cant use,after 2 tries and later the machine just changed. haiz.. i wanted to say if cant use it pls remove the sticker as not to mislead customers but just walk away

why would AMex cont to charge their service more expensive? and make it the least favorite card to be accepted by merchants?

I'll go bonkers if shell doesnt accept amex anymore coz i just changed to shell from petronas 

This is where I use Amex from Statement,

AIRASIA - AK SEPANG MY
CARREFOUR -SRI PETALING KUALA LUMPUR MY
DIGI TELECOMMUNICATIONS AUTO B MY
GSC DATARAN PAHLAWAN MELAKA MY
GSC IOI MALL PUCHONG PUCHONG MY
JUSCO DEPT BDRY MELAKA MELAKA MY
JUSCO SMKT BDRY MELAKA MELAKA MY
MOBIL-DATA PUNCAK ENTERPRPERINGGIT MY
MOBIL-SUN YONG ENG SERVICKUALA LUMPUR MY
NIPPON YATAIMURA JAPANESEPETALING JAYAMY
PARKSON GRAND MAHKOTA PARMELAKA MY
PIZZA HUT-AEON MELAKA MELAKA MY
PIZZA HUT-DESA S.HARTAMASKUALA LUMPUR MY
POH KONG-AEON MELAKA MELAKA MY
RAW NATURE SDN BHD PETALING JAYAMY
SENHENG ELECTRIC - MAHKOTBANDAR MELAKAMY
SHELL - SEC 87 JALAN TAR KUALA LUMPUR MY
TESCO - MELAKA MELAKA MY
TNB AUTOBILLING PETALING JAYAMY
WATSON'S - AEON MELAKA MELAKA MY

next time will use AMEX card to pay GSC ticket nice information.