Stumbled on this really useful script recently which finds the largest tables in a database. I used this on a huge application to work out why the database backup was getting bigger and bigger.

USE [DatabaseNameHere]
GO
CREATE TABLE #temp (
table_name sysname ,
row_count INT,
reserved_size VARCHAR(50),
data_size VARCHAR(50),
index_size VARCHAR(50),
unused_size VARCHAR(50))
SET NOCOUNT ON
INSERT #temp
EXEC sp_msforeachtable 'sp_spaceused ''?'''
SELECT a.table_name,
a.row_count,
COUNT(*) AS col_count,
a.data_size
FROM #temp a
INNER JOIN information_schema.columns b
ON a.table_name collate database_default
= b.table_name collate database_default
GROUP BY a.table_name, a.row_count, a.data_size
ORDER BY CAST(REPLACE(a.data_size, ' KB', '') AS integer) DESC
DROP TABLE #temp