Common parameters can be used with any cmdlet (that means as soon as you mark your function as cmdlet [see CmdletBinding()], you get all of these parameters for free).
Here is the list of all common parameters (alias is in parenthesis after corresponding parameter):
-Debug (db) -ErrorAction (ea) -ErrorVariable (ev) -InformationAction (ia) # introduced in v5 -InformationVariable (iv) # introduced in v5 -OutVariable (ov) -OutBuffer (ob) -PipelineVariable (pv) -Verbose (vb) -WarningAction (wa) -WarningVariable (wv) -WhatIf (wi) -Confirm (cf)