Texas Rangers - Baseball; grew up listening to them on the radio with Mark Holtz calling the games on WBAP 820. Would be outside in the backyard, dad would alternate between grilling and playing catch with me. Favorite of all time.
Dallas Stars - Hockey; hockey is my 2nd favorite sport, so it goes to reason that the Stars are my 2nd favorite team
Dallas Cowboys - NFL; America's Team. What's not to like about them (aside from Jerry Jones and TO
Aston Villa - Football/Soccer; I just like them for some reason.
Dallas Mavericks - I don't care about basketball, otherwise they would be higher.
Other teams I like:
Dodgers, San Diego Padres, Minnesota Wild, Buffalo Sabres. There are more, I just can't think of them right now.