keins davon ist ein Bildformat.

sfx
Self-extracting file archive script (WinRAR)

lfx
?

mbk
Multiple index file backup (dBASE IV)

lft
Laser printer font (ChiWriter)
Loft file (DOS) (3-D Studios)

zik
?

lvl
Miner Descent/D2 Level extension (Parallax Software)

rpg
?

dat
data file (different programs)
Data file (very common) (ASCII or binary)
Error message in inbound internet email message (Microsoft Exchange Server)
MPEG file (various Media Player)
Merge data (WordPerfect)
Word (Microsoft-Word)
KazaA file (KazaA)
QuickTime Install RAM (Quick Time)
geografische Höhenkarte (Empire Earth)
Definitionsdatei für Papierprofile (Nero Cover Designer 2.3)

trk
Script File (Kermit)
Track used by many games (i.e. video sequence)

Dies ist nur ne Liste von bekannten Programmen.
Das muss aber nicht heissen, dass meine Angaben stimmen müssen