Tcode MB51 is one of the most useful Tcode for Material Management in SAP.
It lists all material related transactions which have been done in SAP.
MB51 is quite useful to check the material issued received in any WBS scheme, for creating Asset Transfer Documents (ATDs).
For me it is almost like a debugger, which can be used for tracking everything, finding if any mistakes have been done anywhere in transactions.
Using Filters properly, MB51 is pure magic.