List of SAP Transaction Codes (Cheat Sheet)
When I started to work with SAP I got really mad about all these non-sensical 4 digit transactions and table names. Of course, there are many useful lists on the web, but, for one reason or the other, I could not find one overview, which suits my own needs. So, in a "Slow And Painful" (= SAP?) process, I created my own, including the most important SAP transaction codes (functional and technical). It covers SAP FI, SAP CO, ABAP, the Data Dictionary, and some other SAP basis items. Some examples which are inlcuded in the PDF:
SAP transaction codes (= T-Codes, TC)
| se37 Function module editor | se16 Data Browser | se11 ABAP Dictionary | se80 ABAP repository editor |
| se91 Message maintenance | se24 Class builder | se18 BAdI Definitions | se43 Area Menu maintenance |
| al11 SAP file directory | sci Code inspector | sm58 Transactional RFC | file Logical file path |
| sm56 Number range buffers | sm37 Job Overview | sm36 Job Definition | st22 ABAP Runtime Error (Dump) |
| se09 Transports Organizer | oku4 Translation Tool | sp01 Spool requests | se63 Standard Translation Environment |
| sm35, shdb Batch Input | sm62 Background Events | sm04 User overview | su53 Check authorization data for user |
| fi12 Change House Banks | fbkp Accounting | fbzp Payment Program | ec01 Copy, Check, … Company code |
| ob13 Chart of accounts | ob52 Posting periods | ob29 Fiscal Year Variants | ob57 User -> Tolerance groups |
| fd01 Customer (= Debtor) | fb01 Documents | fk01 Vendor (= Creditor) | fs00 Central G/L accounts |
Please be invited to use this list and/or leave some suggestions for enhancement (see "Disclaimer" for contact information). However, out of experience, allow me to make one stipulation: although this cheat sheet is freely available, please refrain from uploading it to other servers.
The items are categorized: ABAP, Data Dictionary, FI (Accounting, General Ledger), CO (Controlling), Spool, Archive Development Kit (ADK), BAdI, runtime, transport management, authorization, translation, logs etc.).
Below is a screenshot of the pdf, to show an overview of the structure (the list contains both customizing and operational transaction codes):

Please feel free to download the corresponding 1 page cheat sheet » SAP Transaction Codes (T-Code) as PDF (approx. 100 KB).
SAP Modules (standard business applications)
FI - Financial Accounting
CO - Controlling
EC - Enterprise Controlling
TR - Treasury
AA - Asset Accounting
SD - Sales and Distribution
MM - Materials Management
PM - Plant Maintenance
PP - Production Planning
HR - Human Resource
IM - Investment Management
LES - Logistics Execution System
EHS - Environment, Health & Safety
SCM - Supply Chain Management
PLM - Product Lifecycle Management
SRM - Supplier Relationship Management
BP - Business Partner
CML - Consumer & Mortgage Loans
CMS - Collateral's Management System
QM - Quality Management
BW - Business Warehousing
WCM - Web Content Management
WCM - Work Clearing Management
EP - Enterprise Portal
Industry Solutions - (IS-) Prefix
IS-U - Utilities
IS-R - Retail
IS-T - Telecommunication
IS-H - Health
IS-M/AM - Media / Advertising Management
SMB - Small Midsize Business
LSMW - Legacy System Migration Workbench
CS - Customer Service
CA - Cross Application Components
PS - Project Systems
PI - Process Integration (f.k.a. XI)
Financial Services (FS-) Prefix
FS-CM - Claim Management
FS-PM - Policy Management
FS-CD - Collection & Disbursement
FS-ICM - Incentive / Commission Management
FS-RI - Reinsurance
Proverbs & Idioms & Sayings