World War I, World War II, Korea, Viet Nam, Gulf War and the wars in the Middle East. The most current conflicts should be accessible from the source - the servicemen and women involved.
The World Wars, Korea and Viet Nam: Ancestry.com has collections of enlistments, casualties, burials and similar records. Fold3 will also have pertinent collections. The NARA should have service records, although, I believe, some of the 20th century records have been destroyed.
That takes us to the end of the military record review.
My ancestors contributed to the Colonial Wars, French and Indian War, Revolutionary War, Barbary Wars, War of 1812, Texas Independence [Alamo], Civil War, Philippines & WWII. In some cases, they were direct line; in others, near or distant cousins or uncles.
With one exception, the Alamo, all came out alive. A few were wounded or contracted diseases that would eventually contribute to their deaths. Still, they all served!
My girlfriend and I recently went to Branson, MO for a weekend. The shows wrap-up with military tributes - Marine Corps, Army, Navy, Air Force and Coast Guard anthems. More places should do the same.