SUMMARY: This is really long, so I'll summarize real quick. People complain that fighters in 5e are boring, but that's because they're not being creative. The rules make it easy to do anything you can think of, more or less; you just need to think like a warrior. I give some examples of things the current rules support.
EDIT - I also posted this on reddit, phrased differently on some places. Just FYI.
Now then. One of the main complaints I see with the 5e playtest is that fighters are dull to play. Just hack and slash and move on, with nothing cool happening. I've read that fighters have no cool abilities. That's incorrect--fighters have almost any cool ability you can think of. Since rolls are now based on stats, not skills, a fighter will excel at anything that uses strength. This is an amazing system--you don't have to train or take feats to do anything other than swing a sword like in other versions. You don't look at your list of abilities to decide what you're allowed to do. You use your imagination, and then you DO IT.
This is a result of two things: Advantage and Contests.
Advantage means that any interesting maneuvering on your part has an immediate benefit, if you're successful. ANY INTERESTING MANEUVERING. Think about that for a second.
Contests cover basically ANYTHING that isn't a direct weapon attack. There are a lot of things that happen in combat that aren't direct weapon attacks.
Also, take note of the Improvise section of the How to Play guide. It more or less backs me up here.
One last note before the interesting stuff: 5e has absolutely nothing in it that should lead to a Mother-may-I experience. Never ask the DM if you are allowed to do something. You simply say you're going to try it, he assigns a DC (if applicable) and you roll. The end. Don't ask for permission, and if you're DM, don't expect to be giving it. Empower the players.
I'm giving you a list of things that could reasonably be done under the current rules that will make a fighter an interesting and dynamic thing to be. Keep in mind that you can only do one thing per round, so I usually make the advantage roll take effect on the turn afterward. This is all stuff for a player to come up with on the fly. My player will say 'I'm going to trip him,' and I as DM improvise how that might work. None of these ideas are intended to become new rules, or even act as such. It's more about helping players think like a warrior, and helping DMs accommodate them. If you don't like how I ruled it, rule it differently in your game. NEVER TELL A PLAYER NO. They can try whatever they want, and the rules let that happen.
1 - Choke. Attacker has disadvantage and must use a free hand, but on successful hit, str contest to choke. Success causes restrained. Contest each round to maintain, and after three successful rounds, next round causes stunned. Next round causes unconscious. Death ten rounds later (which is actually too short in real life). Come here, goblin! (A fighter within arm's reach of a mage will probably never lose, which I and my players have generally been happy about.)
2 - Lock Joints. Again, attacker has disadvantage, needs two free hands. Str or dex contest, depending on circumstances and DM whim. Success causes restrained. I usually only give the defender one attempt to break the hold.
3 - Disarm. Attacker has disadvantage, successful hit triggers dex contest to disarm.
4 - Trip. Dex or Str contest, depending. This could be anything from a sweep attack to a bullrush and lifting up the enemy. Attacker gets advantage if the halfling is ducked down behind the target, giving him something to trip over :D Once tripped, target is prone.
5 - Throw net. I know it's not on the EQ list. Make one. Then throw it. Successful hit causes restrained. Then toss an Alchemist's Fire for extra fun. After dumping oil on them.
6 - This is really one for the rogue, but I had a player manacle an enemy's legs with two hidden attacks.
7 - Oil up the floor and make the enemies fight while standing on it.
8 - As a ready action, duck under a strike and end up behind the enemy, ready to hit him from behind next round. Gave that a dex DC of 17.
All of those were improvised on the spot, and the rules made it very easy to accommodate. Here are some other things that were tried or talked about (I'm sparing the rules I used since by now I think you have the idea):
Launch the halfling over an enemy. Throw a goblin to knock another goblin over. Make and throw mud. Gouge out eyes. Knock away the enemy's shield, giving the next person to hit them advantage. Throw **** (yes, that happened.) Hold the end of a rope for the thief to walk across like a tightrope. Dwarf, grab that ogre's nuts.
One last thing. This isn't really about the rules or covered by them in any DnD system of which I'm aware, but I do it to make things more fun. Sometimes when an enemy is brought to 0 hitpoints, instead of killing them, I make them combat incapable but still conscious. For example, "Your greataxe cuts right through both of the orc's knees, severing them and dropping him to the ground screaming." The legless orc might then, for example, flop around and get in the way, still try to swing his sword, lay about screaming in pain, beg for mercy, or who knows what. The party then may do roleplay-ey sorts of things involving the orc if they wish. Basically, it still meets the spirit of the rules, but it gives the party a better sense that they're interacting with the world than simply 'You killed it to death. It dies.' Other things are cut off an enemy's sword arm, causing him to yield; disembowel something large, causing its guts to spill all over and make the ground slick, etc.