I know I cheated in a few places, I hope you'll forgive me.
1. Blame
They rounded the corner at an all out sprint, an angry mob right at their heels – the Master blamed the Doctor for it entirely.
2. Proof
Every time the Doctor woke up the Master would be tucked tightly against him, clinging to him as though he thought he'd disappear; it was all the proof he needed that the Master loved him.
3. Assistance
"Please Master, I can't do this without you."
4. Going
The first time they ever really fought the TARDIS had to make an emergency landing as the Master stormed off, uncaring if he stepped out into the void.
5. Birthday
The Master always celebrated the Doctor's birthday but he never celebrated his own; that stopped tonight.
6. Scientist
If another scientist tried to experiment on the Doctor the Master was going to make the planet burn.
7. Silent
After a particularly nasty fight the Master remained silent for a full day, not even bothering to mock the Doctor when he went out of his way to do something ridiculous in an attempt to draw him out.
8. Behalf
The first time the Master got in a fight on the Doctor's behalf, the Doctor went weak at the knees, knowing it was the purist way for the Master to express his love.
9. Rumor(ed)
The Master only ever heard rumors about a woman named 'Rose'; he often wondered if the Doctor could ever love him as much, or if he'd always be the runner up.
10. Tip
Sometimes the Doctor tipped humans, just to make sure they left the Master alone.
11. Idle
The drums never let the Master stay idle for long; sometimes the Doctor fucked the Master hard into the mattress just to help him sleep through the night.
12. Brother
The Master thought Jack was the closest thing the Doctor had to a brother, so he was the first the Master approached when he decided to propose.
13. Beneath
No matter how much the Doctor loved them, the Master would always know that humans were below them.
14. Redecorate
The Master was used to keeping things in basic, spartan conditions; now that they have each other, the Doctor gently helped him collect personal items that he could genuinely call his own.
15. Gravitation
The Master swore the Doctor had his own gravitational pull, and no matter how hard he tried to stay away he kept getting drawn back; he knew that one day this would kill him.
16. Kilt
The Doctor shifted self consciously, "How do my calves look?"
17. Afterthought
When the Dalek's finally killed the Doctor the Master lost his mind, and found himself stuck in a red haze; killing was almost an afterthought.
18. Unearth
The Doctor loved it when the Master let him sift through his mind; he treasured everything he unearthed.
19. Shield
The Doctor always knew when they were in real trouble; the Master would automatically shift until he stood in front of the Doctor, acting as a shield.
20. Blacklist
The Doctor loved to make the Master happy, even if it meant getting blacklisted from certain clubs, restaurants, and occasionally a planet.
21. Misquoted
The Master couldn't believe the Doctor would say something so hurtful; what was worse, he didn't even seem to know what he'd done.
22. Copying
The Doctor could tell whenever the Master was actually trying to make a good impression; he would always start unconsciously copying the Doctor's movements.
23. Argue/Arguing
Sometimes it was hard to visit his old companions; they always started an argument about his relationship with the Master the moment they were alone.
24. Lens
The Master knew the Doctor didn't really need to wear glasses, but it was still adorable to see him in them.
25. Bell
Sometimes the Master would disappear into the depths of the TARDIS, only to leap out hours later, scaring the daylight out of him; he decided to put a bell on him, and then got lost in thoughts of the Master in a collar.
26. Arrest(ed)
For his birthday Amy dressed in her old police uniform and pretended to arrest the Master; the Doctor stole the cuffs.
27. Havoc
Creating havoc was one of the Master's many talents.
28. Tool
The Master had a screwdriver between his lips, a set of wire clippers in his hand, and grease smudged on his cheek as he ran maintenance on the TARDIS; it was one of the hottest things the Doctor had ever seen.
29. Blanket
Cuddling on the couch was the Doctor's favorite thing to do; he found himself wishing he could make those moments last forever.
30. Fancy
The Master loved crashing fancy dinners, which was a pity since he looked so good in a tux.
31. Dash
The Doctor grabbed his hand with a boyish grin and whispered, "Run!"
32. Away
Whenever the Master got into a particularly dark mood, the Doctor would take him far away, until they found planets with as little life as possible to make love in.
33. Syndication
"No, we are not forming the "Time Lord Detective Agency," I don't care if we'd be better than Scooby Doo!"
34. Champagne
The Master refuses to drink anything but champagne whenever they visit Earth; the Doctor is sure he does this only because he likes the glasses they're served in.
35. Note
The Doctor often finds sweet notes hidden around the TARDIS in circular Gallifreyan.
36. Physical
When the Master got really sick the Doctor insisted they visit a doctor; the Master whined the whole way.
37. Dull
While the Master was very good at coming up with plots to take over the universe, he was terrified the Doctor would find him extremely dull after seeing him every day.
38. Frozen
The Master was dozing on the beach when the Doctor slid an ice cube down his stomach, laughing as the Master giggled and squirmed.
39. Stumble(d)
The Master whispered 'I love you,' and the Doctor stumbled, nearly smacking his head against the side of a building.
40. Hunt
For their anniversary the Master took the Doctor out to hunt hunters with paintball guns; afterward they ran with the deer through the forest.
41. Gibberish
The Master was delirious with fever, mumbling things the Doctor didn't understand, though he was fairly certain he heard his name more than once.
42. Camp
The Master didn't understand the purpose of going camping when they could just take the TARDIS anywhere they wanted, but the Doctor was dead set on taking him.
43. Weak(ness)
Love was a weakness, but the Master couldn't resist.
44. Bargain
The Master never begged in bed, he bargained.
45. Alcohol
The Master had never been in a long term relationship before – when he thought he finally fucked it up for good, he found a bar planet and drank and drank and drank until he finally blacked out.
46. Wind
The Doctor liked to let the wind run through his hair; the Master liked to watch.
47. Temptation
The Master liked to sleep naked, stretched out like a cat on top of the Doctor's bed; it was a temptation the Doctor could never resist.
48. Eighteen
Sometimes the Master dreamed of an eighteen year old Doctor; Theta Sigma was his first love.
49. Bottle
The Doctor wanted to bottle the Master's scent so he could keep it in the heart of the TARDIS forever.
50. Rhythm
The drums are faint in the Master's mind when the Doctor is around, but he'll never forget their rhythm.