BAPI Explorator BAPI
BAPI45 Browser BAPI
BAPIW Explorator BAPI
OS01 LAN checkk: verify LAN by ping
SE14 Utilities for Dictionary tables
SE15 System Info Dictionary
SE16 Data browser. List tables. With * in 'Table Name' list all tables
SE37 ABAP function modules
SE38 ABAP editor
SE80 Object Navigator
SE93 Find code-T. Other option: code-T SE16 + table TSTC display records.
SLG1 System logs
SM02 System messages
SM04 User list
SM05 HTTP session management: monitoring
SM12 List lock entries in a SAP system. To see all the locks press F8 or button with literal "List"
SM37 See active transaction background
SM50 To check process overview of active servers
SM59 RFC Destinations (Display/Maintain)
SM66 Global work process overview
ST22 ABAP runtime errors - All clients