"Gatha" (Verse) on mindfulness/contemplation of Death : Ven. Mahasi Sayadaw Practice : Ven. Mahasi Sayadaw

Is there any "Gatha" (Verse) can be used to contemplate on "Death"?
The purpose is to use as an aid to generate necessary energy to continue practice [mostly as the first thing in the morning]
Because you mention the Mahasi Sayadaw in your question, most relevant is the Mahasi Sayadaw's discussion of the Purabheda Sutta:

http://static.sirimangalo.org/mahasi/Purabheda%20Sutta.htm

(Sorry, the formatting is off in this version)

There are some Pali phrases in that book that might be of interest, e.g.:


  Vītataṇho purābhedā, pubbamanta manissito.
  Vemajjhe nupasaṅkheyo, tassa natthi purekkhataṃ.
  
  The one who has removed craving before death, independent of past and future;
  who is not stuck in the present; for such a one there is no further becoming.




Also in the Mahasi Sayadaw tradition, it is customary to reflect on death before starting the practice:


  The fourth protection for your psychological benefit is to reflect on the phenomenon of 
  ever-approaching death. Buddhist teachings stress that life is uncertain, but death is 
  certain; life is precarious but death is sure. Life has death as its goal. There is birth, 
  disease, suffering, old age, and eventually, death. These are all aspects of the process of 
  existence.
  
  -- Mahasi Sayadaw, Practical Insight Meditation


The Pali for this is from the Dhammapada Commentary:


  addhuvaṃ me jīvitaṃ, dhuvaṃ me maraṇaṃ
  
  My life is unsure; my death is sure.
  
  avassaṃ mayā maritabbameva, 
  
  Indeed, in the future I must die. 
  
  maraṇapariyosānaṃ me jīvitaṃ, 
  
  My life has death as its final end.
  
  jīvitameva aniyataṃ, maraṇaṃ niyatanti 
  
  Life indeed is uncertain, death is certain.
  
  -- Dhp-A 174 (pesakāradhītāvatthu)


These are often chanted before starting a meditation course in the Mahasi Sayadaw tradition.



Besides this, there are many verses about death in the tipitaka; the most common is that spoken by Sakka when the Buddha passed away:


  “aniccā vata saṅkhārā, uppādavayadhammino.
  uppajjitvā nirujjhanti, tesaṃ vūpasamo sukho”ti.
  
  Impermanent indeed are all formations; of a nature to arise and pass.
  Having arisen, they cease; their fading away is happiness.
  
  -- DN 16


Another similar one we use often is Dhp 41:


  aciraṃ vatayaṃ kāyo, pathaviṃ adhisessati.
  chuddho apetaviññāṇo, niratthaṃva kaliṅgaraṃ.
  
  In no long time indeed will this body lie on the earth;
  Discarded, consciousness having departed, as useless as a charred log.