Roll here on a natural 1 attack roll.

d20	Effect
1	Great recovery, get free attack with double damage.
2	Lose next attack. Better luck next time .
3	In enthusiasm, hit self. Take 1 hp.
4	Dodge back 5 feet, regardless of whats there.
5	Must parry next round .
6	Drop Weapon, 1 round to regain it.
7	Clumsy move. Attack next round at -4 to hit.
8	Shield knocked aside, no shield bonus next round.
9	If wearing plate armour, random bit comes loose. AC penalty of 1 until you spend a round fixing it.
10	Enemy hits backpack or pouch, random item must save vs. crushing blow.
11	Hit person to right of target. -4 on to hit roll.
12	Weapon goes flying 10 feet in random direction.
13	Off balance for 1 round. Enemy gets +2 to hit.
14	You let enemy get inside your weapon range, you miss 1 attack and he gets +2 to hit.
15	Money or spell component pouch knocked free, contents go flying everywhere.
16	Pull muscle, -1 to hit for rest of fight.
17	Weapon must save vs. crushing blow or break.
18	Fall on face, spend next round recovering. Opponent gets +4 to hit.
19	Weak parry, enemy gets 1 free attack.
20	Walk into enemies attack. He gets +2 to hit and does double damage.