1. Adrenaline (boost melee damage die by one step when below half health).
2. Weathered ol' Bastard (+1 AC, +2 to saves versus the elements).
3. Ravenous Hatred (Name a thing you fought that harrowed you, you get +2 to hit and boost your damage die when you deal with them).
4. No Train Left Unsuplexed (Once per day, you can attempt a feat of strength otherwise considered impossible by the DM). Thanks to Claytonian for inspiring this one.
5. War Cry (Once per day, you may let out a fearsome yell that causes 1d6+level foes with a HD equal to your level to Save or flee/surrender).
6. Gunslinger/Crossbowman (You have a knack for crossbows/guns. Instantly reload your weaponry).
7. Thaumaturgical Tennis (You can attempt to strike back magic with your sword once per day with an additional use every third level. Yes. You must declare this, then attempt to strike the magic with your weapon. The DM will decide the difficulty number, I'd do either 10+the caster's level or 10+twice the spell level. If it works, it is sent back to them and they must deal with it as normal).
8. ATATATATATATATATATA and so on (Once per day, you can do half your level in additional strikes).
1. Marked for Death (You are cursed by... something. -1 to Death Saves per two levels, you also shiver at night from an unearthly cold).
2. Shaky Hands (-1 to hit and -1 to initiative, assuming a d6 based initiative system, with all ranged weaponry. Please explain why you are like this).
3. Traumatized (Remember those goblins that fucked up your party? You need to pass fear saves to deal with a certain type of creature or foe that has tormented you before).
4. The Will is Strong but the Flesh... (You heal at half the rate, including magical means).
5. OH NO, IT'S MY RIVAL/SHADOW REALM DOUBLE/SIBLING! (You have an exceptionally arrogant and/or haughty rival. They are a level above you but they generally prefer to smugly vex you instead of outright killing you. Unless circumstances permit otherwise, of course).
6. You'll Wish You Were Marked for Death (Your favourite NPC/Pet/hireling/lover? They're going to die. In 1d6 adventures' time. The DM rolls secretly but they can foreshadow it clearly if they wish).
7. Bent Double, Like Old Beggars Under Sacks (Your encumbrance limit is halved, rounded up).
8. DON'T GO OUTSIDE AT NIGHT (Seriously, don't. Something's waiting especially for you).
Optionally, if you find these drawbacks too harsh you could allow the player to attempt to complete a perilous quest or journey to find a solution.